UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 1)*

PAR PETROLEUM CORPORATION

(Name of Issuer)

Common Stock, $0.01 par value

(Title of Class of Securities)

69888T108

(CUSIP Number)

Jonathan D Wasserman, Esq.

Equity Group Investments

2 North Riverside Plaza, Suite 600

Chicago, Illinois 60606

312-466-3505

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

June 14, 2013

(Date of Event which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of ss. 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box  ¨.

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See ss. 240.13d-7(b) for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

POTENTIAL PERSONS WHO ARE TO RESPOND TO THE COLLECTION OF INFORMATION CONTAINED IN THIS FORM ARE NOT REQUIRED TO RESPOND UNLESS THE FORM DISPLAYS A CURRENTLY VALID OMB CONTROL NUMBER.

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EXPLANATORY NOTE: This Amendment No. 1 to Schedule 13D (“Amendment No. 1”) relates to the Common Stock, $0.01 par value per share (the “Common Stock”) of Par Petroleum Corporation, a Delaware corporation (the “Issuer”), which has its principal executive office at 1301 McKinney, Suite 2025, Houston, Texas 77010. This Amendment No. 1 amends and supplements, as set forth below, the Schedule 13D filed by the Reporting Persons with respect to the Issuer on September 10, 2012 (the “Schedule 13D”). All capitalized terms not otherwise defined herein have the meanings ascribed to such terms in the Schedule 13D. The Schedule 13D is amended and supplemented by adding the information contained herein, and only those items amended are reported herein.

Item 3 of the Schedule 13D is hereby amended and supplemented as follows:

As further described in Item 4 below, on June 14, 2013, Holdings and certain other accredited investors (each an “Investor” and collectively, the “Investors”) entered into a commitment letter with the Issuer (the “Commitment Letter”) pursuant to which the Investors committed to purchase from the Issuer, in connection with the Acquisition (as defined in Item 4 below), an aggregate of $200,000,000 of shares of Common Stock of the Issuer at a price of $1.39 per share in a private placement transaction. Pursuant to the Commitment Letter, Holdings has committed $62.3 million for the purchase of 44,829,205 shares of Common Stock of the Issuer. The source of the funds for this purchase will be cash on hand and capital contributions to the Master Fund.

Item 4 of the Schedule 13D is hereby amended and supplemented as follows:

On June 17, 2013, a wholly-owned subsidiary (the “Buyer”) of the Issuer entered into a membership interest purchase agreement (the “Purchase Agreement”) with Tesoro Corporation, a Delaware corporation (the “Seller”), and solely for the limited purposes set forth in the Purchase Agreement, Tesoro Hawaii, LLC, a Hawaii limited liability company (“TSO Hawaii”). Pursuant to the Purchase Agreement, Buyer will purchase from the Seller (the “Acquisition”) all of the issued and outstanding units representing the membership interests in TSO Hawaii (the “Purchased Units”), and indirectly TSO Hawaii’s wholly owned subsidiary, Smiley’s Super Service, Inc., a Hawaii corporation (the “Acquired Subsidiary”). TSO Hawaii and the Acquired Subsidiary own, operate and use (i) a petroleum refinery located at the Campbell Industrial Park in Kapolei, Hawaii, (ii) certain pipeline assets, floating pipeline mooring equipment, and refined products terminals, and (iii) retail assets selling fuel products and merchandise on the islands of Oahu, Maui and Hawaii.

In connection with the Acquisition, the Issuer has proposed to make a private placement (the “Offering”) of $200,000,000 of shares of Common Stock to the Investors pursuant to an exemption from registration provided in the Securities Act of 1933, as amended (the “Securities Act”). The proceeds of the Offering will be used by the Issuer to fund the Acquisition, to repay indebtedness outstanding and other obligations under the Issuer’s Delayed Draw Term Loan Credit Agreement dated as of August 31, 2012 (as amended, amended and restated, modified, supplemented, extended, renewed, restated or replaced from time to time) and for working capital and general corporation purposes of the Issuer and its subsidiaries. As described in Item 3 above, Holdings has committed $62.3 million for the purchase of 44,829,205 shares of Common Stock in the Offering. The Offering will close upon the satisfaction of certain conditions, including the negotiation, execution and delivery of definitive documentation with respect to the Offering, the consummation of the Acquisition, obtaining all necessary board of directors, stockholder, third party and other approvals of the Offering, and the amendment of certain provisions of the Issuer’s Amended and Restated Certificate of Incorporation, the Warrant Issuance Agreement dated August 31, 2012 (the “Warrant Agreement”) and the Registration Rights Agreement dated August 31, 2012 (the “Registration Rights Agreement”).

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The Reporting Persons currently own, and upon closing of the Offering, expect to own the Common Stock solely for the purpose of investment and intend to review this investment on a continuing basis. Depending on various factors, including but not limited to each Reporting Person’s business, financial position, strategic direction and prospects, price levels of the Common Stock, conditions of the securities markets, and general economic and industry conditions, each of the Reporting Persons may in the future take such actions with respect to its investment in the Issuer as it deems appropriate, including but not limited to changing its current intentions, with respect to any or all matters required to be disclosed in this Schedule 13D, as amended. Without limiting the foregoing, each Reporting Person may, from time to time, acquire or cause affiliates to acquire additional Common Stock, dispose of some or all of its Common Stock (including sales pursuant to the Registration Statement and the terms of the Registration Rights Agreement described in Item 6 hereto), or continue to hold Common Stock (or any combination or derivative thereof). In addition, without limitation, the Reporting Persons, in their capacity as stockholders, may directly or indirectly engage in discussions with members of management, directors, and stockholders of the Issuer and other parties, concerning extraordinary corporate transactions (including but not limited to a merger, reorganization or liquidation) relating to the Issuer as well as concerning its business, operations, assets, strategy, future plans, prospects, corporate structure, board composition, management, capitalization, dividend policy, charter, bylaws, corporate documents and agreements. As a result, the Reporting Persons may take positions with respect to and seek to have the Nominee Directors influence the decision of the Board regarding the matters discussed above. Except as set forth herein, or as would occur upon completion of any of the matters discussed herein, no Reporting Person has any present plans or proposals that would relate to or result in any of the matters set forth in clauses (a) through (j) of Item 4 of Schedule 13D; provided that each Reporting Person may, at any time, review or reconsider its position with respect to the Issuer and reserves the right to develop such plans or proposals.

Item 5 of the Schedule 13D is hereby amended and supplemented as follows:

(a) and (b) To the best knowledge of the Reporting Persons, there were 151,823,993 shares of Common Stock outstanding on May 3, 2013, based on the Issuer’s Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2013.

Each of Master Fund and General Partner is deemed to be the beneficial owner of 56,359,319 shares of Common Stock, or approximately 36.2% of the issued and outstanding shares of Common Stock as of May 3, 2013, and Master Fund shares voting and dispositive power with General Partner with respect to such shares. The 3,959,328 shares of Common Stock issuable upon exercise of the Warrants held by Holdings are included in the beneficial ownership calculation in the preceding sentence. Holdings shares voting and dispositive power with Master Fund and General Partner with respect to the 3,959,328 shares of Common Stock issuable upon exercise of the Warrants, or approximately 2.5% of the issued and outstanding shares of Common Stock as of May 3, 2013. No other person referenced in Item 2 of the Schedule 13D beneficially owns any shares of Common Stock.

(c) Except as set forth in Item 3 and Item 4 above, during the last 60 days, no transactions in the Common Stock were effected by the Reporting Persons.

(d) No person other than the Reporting Persons has the right to receive or to direct the power to receive dividends from, or the proceeds from the sale of shares of Common Stock owned by the Reporting Persons.

Item 6 of the Schedule 13D is hereby amended and supplemented as follows:

Pursuant to the Commitment Letter described in Items 3 and 4 above, Holdings has committed to invest $62.3 million for the purchase of 44,829,205 shares of Common Stock of the Issuer. Exhibit A to the Commitment Letter sets forth the terms and conditions of the Offering. Pursuant to Exhibit A to the Commitment Letter, as soon as reasonably practicable after the closing of the Offering, but no later than sixty calendar days after such closing, the Issuer will prepare and file a registration statement on Form S-1 for the resale of the shares sold in

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the Offering (the “Registration Statement”). The registration rights provided for in Exhibit A to the Commitment Letter will not be more favorable in any material respect than or otherwise inconsistent with the registration rights granted under the Issuer’s Registration Rights Agreement, and the “holders” under such Registration Rights Agreement shall be treated pari passu or with priority with respect to the Investors and have priority over the Investors.

Under Exhibit A to the Commitment Letter, in order to effectuate the intents and purposes of the Commitment Letter, each of the Investors has agreed to vote their shares of Common Stock, if any, in favor of, or otherwise consent to, certain amendments to (i) the Issuer’s Amended and Restated Certificate of Incorporation to increase the amount of authorized shares and to allow the Issuer’s board of directors to approve certain transfers of Common Stock by 5% investors; (ii) the Warrant Agreement, in order to waive the application of anti-dilution rights provided in the Warrant Agreement with respect to the shares issued in the Offering; and (iii) the Registration Rights Agreement in order to waive the application of piggyback registration rights under such agreement with respect to the Registration Statement covering the shares issued in the Offering.

The Commitment Letter contains representations from each Investor as to such Investor’s status as an accredited investor and such Investor’s level of financial sophistication. The Commitment Letter also contains other customary terms and conditions, including provisions regarding payment of fees and expenses in connection with the Offering and indemnification.

The description of the Commitment Letter contained in this Item 6 is not intended to be complete and is qualified in its entirety by reference to such agreement, which is attached as Exhibit E and incorporated by reference herein.

ITEM 7. Material to be Filed as Exhibits.

Exhibit E: Commitment Letter, dated June 14, 2013

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SIGNATURES

After reasonable inquiry and to the best of the undersigned’s knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.

DATED: June 27, 2013

Exhibit E

Commitment Letter

CONFIDENTIAL

June 14, 2013

Par Petroleum Corporation

1301 McKinney, Suite 2025

Houston, Texas 77010

Attention: R. Seth Bullock

Private Placement of $200,000,000 of Shares of Common Stock

Ladies and Gentlemen:

1.         Acquisition. Reference is made to the Membership Interest Purchase Agreement, dated as of June 17, 2013 (the “MIPA”), by and among Hawaii Pacific Energy, LLC,a Delaware limited liability company (“Buyer”), Tesoro Corporation (“Seller”), Tesoro Hawaii, LLC (“Target”) and Par Petroleum Corporation, a Delaware corporation (“you” or the “Company”), pursuant to which Buyer will acquire all of the issued and outstanding equity interests of Target from Seller (the “Acquisition”).

2.         Private Placement. In connection with the Acquisition, the Company is proposing to make a private placement (the “Offering”) of $200,000,000 of shares of the Company’s common stock (“Common Stock”), par value $0.01 per share, to institutional accredited investors pursuant to the exemptions from registration provided in the Securities Act of 1933, as amended (the “Securities Act”).

3.         Commitment. Each of the undersigned investors (the “Investors”) is pleased to offer the Company its binding commitment and agreement to purchase in the aggregate $200,000,000 of shares of the Common Stock in the Offering, at a price of $1.39 per share, as set forth on the commitment schedule attached hereto (the “Commitment”), for the purposes and upon and subject to the terms and conditions set forth in this letter (this “Commitment Letter”) and in the Summary of Terms and Conditions attached as Exhibit A hereto and incorporated herein by this reference (the “Summary of Terms”). This Commitment Letter is being delivered to you to induce the Company and Buyer to enter into the MIPA. Each Investor’s commitment to purchase under this Commitment Letter is several and not joint; for the avoidance of doubt, references in this Commitment Letter to the Investors and to the rights and obligations of the Investors shall be deemed to refer to each of the Investors individually and not jointly.

4.         Investment Representations. Each Investor represents severally and not jointly that such Investor: (a) is an “accredited investor” as defined in Rule 501(a)(1), (2), (3), (5), (6), (7) and/or (8) of Regulation D under the Securities Act; (b) has such knowledge, sophistication and experience in business and financial matters so as to be capable of evaluating the merits and risks of the Commitment and the shares of Common Stock contemplated thereby, and has so evaluated the merits and risks of the Commitment; (c) been given access to and an opportunity to examine such documents, materials and information concerning the Company, the Target and the Acquisition as the Investor deems to be necessary or advisable in order to reach an informed decision as to an investment in the Company, to the extent that the Company possesses such information, has carefully reviewed and understands these materials and has had answered to the Investor’s full satisfaction any and all questions regarding such information; (d) made such independent investigation of the Company, its management, and related matters as the Investor deems to be necessary or advisable in connection with the Commitment, and is able to bear the economic and financial risk of the Commitment and the shares of Common Stock contemplated thereby; (e) has not been offered the shares of Common Stock contemplated by the Commitment by any means of general solicitation or general advertising; and (f) were solicited or became aware of this investment either

through (1) a substantive, pre-existing relationship with the Company, (2) direct contact with the Company or its agents outside of any public offering effort, and/or (3) through contacts by the Company not identified through any public offering.

5.         Use of Proceeds. The proceeds of the Commitment will be used by the Company (a) to fund the Acquisition, (b) to repay indebtedness and other obligations of the Company and its affiliates outstanding under the Company’s Delayed Draw Term Loan Credit Agreement dated as of August 31, 2012 (as amended, amended and restated, modified, supplemented, extended, renewed, restated or replaced from time to time, (the “Exit Facility”), and (c) for working capital and general corporate purposes of the Company and its subsidiaries.

6.         Conditions. The Commitment shall be subject to consummation of the Acquisition substantially consistent with the terms of the MIPA.

7.         Reimbursement of Fees and Expenses. By executing this Commitment Letter, you agree to reimburse the Investors from time to time on demand for all reasonable out-of-pocket fees and expenses (including, but not limited to, the reasonable fees, disbursements and other charges of counsel to the Investors) incurred in connection with the preparation and negotiation of the definitive documentation for the Offering and the consummation of the transactions contemplated hereby and thereby.

8.         Confidentiality. This Commitment Letter and the contents hereof and thereof are confidential and, except for disclosure hereof or thereof on a confidential basis to your accountants, attorneys and other professional advisors retained by you, Buyer, Seller, or Target in connection with the MIPA and the Acquisition or as otherwise required by law, may not be disclosed in whole or in part to any person or entity without our prior written consent; provided, however, that nothing shall prevent or delay you or the Investors from disclosing this Commitment Letter and the contents hereof as required by applicable law; provided, further, that the disclosing party shall provide a copy of any such required disclosure to the non-disclosing party prior to any public disclosure. You acknowledge that the Investors or their affiliates may be providing financing or other services to parties whose interests may conflict with yours. Each Investor agrees to not disclose confidential information obtained from you, except as contemplated by the provisos in the preceding sentence, and that we will treat confidential information relating to you and your affiliates with the same degree of care as we treat our own confidential information.

9.         Parties in Interest; Third Party Beneficiaries. This Commitment Letter is for the sole benefit of and shall be binding upon the Company and the Investors and their respective successors and permitted assigns. Nothing in this Commitment Letter, express or implied, is intended to or shall confer upon any person other than the Company, any legal or equitable right, benefit or remedy of any nature whatsoever, under or by reason of this Commitment Letter. In no event shall this Commitment Letter or the Commitment hereunder be enforced by any person unless each of the other unfunded Commitments hereunder are being concurrently enforced by such person. Notwithstanding anything to the contrary in this Commitment Letter, the aggregate liability of each Investor hereunder shall not exceed the amount set forth opposite such Investor’s name on Schedule of Commitments attached hereto.

10.       Termination. The obligation of the Investors to fund the Commitment will terminate automatically and immediately upon the earliest to occur of (a) the valid termination of the MIPA in accordance with its terms, (b) the closing of the Offering, at which time the obligation will be fulfilled, or (c) September 30, 2013.

11.       Survival. The provisions of Sections 7, 8 and 9 shall remain in full force and effect regardless of whether any definitive documentation for the Offering shall be executed and delivered, and shall survive notwithstanding the termination of this Commitment Letter.

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12.       Severability. If any term or provision of this Commitment Letter is invalid, illegal or unenforceable in any jurisdiction, such invalidity, illegality or unenforceability shall not affect any other term or provision of this Commitment Letter or invalidate or render unenforceable such term or provision in any other jurisdiction; provided, that if the obligation to fund the Commitment under this Commitment Letter is unenforceable with respect to any Investor, it shall be unenforceable with respect to all Investors.

13.       Amendment. This Commitment Letter may only be amended, modified or supplemented by an agreement in writing signed by each party hereto.

14.       Governing Law. This Commitment Letter shall be governed by and construed in accordance with the internal laws of the State of Delaware without giving effect to any choice or conflict of law provision or rule (whether of the State of Delaware or any other jurisdiction).

15.       WAIVER OF JURY TRIAL. EACH PARTY ACKNOWLEDGES AND AGREES THAT ANY CONTROVERSY WHICH MAY ARISE UNDER THIS COMMITMENT LETTER IS LIKELY TO INVOLVE COMPLICATED AND DIFFICULT ISSUES AND, THEREFORE, EACH SUCH PARTY IRREVOCABLY AND UNCONDITIONALLY WAIVES ANY RIGHT IT MAY HAVE TO A TRIAL BY JURY IN RESPECT OF ANY LEGAL ACTION ARISING OUT OF OR RELATING TO THIS COMMITMENT LETTER OR THE TRANSACTIONS CONTEMPLATED HEREBY.

16.       No Assignment. The Commitment evidenced by this Commitment Letter shall not be assignable by the Company or any Investor (other than to an affiliate of any such Investor, which shall not be restricted hereunder) without each Investor’s prior written consent, and the granting of such consent in a given instance shall be solely in the discretion of each Investor. Any purported assignment of this Commitment in contravention of this Section shall be void.

17.       Counterparts. This Commitment Letter may be executed in counterparts, each of which shall be deemed an original, but all of which together shall be deemed to be one and the same agreement. A signed copy of this Commitment Letter delivered by facsimile, e-mail or other means of electronic transmission shall be deemed to have the same legal effect as delivery of an original signed copy of this Commitment Letter.

THIS WRITTEN AGREEMENT (WHICH INCLUDES THE SUMMARY OF TERMS) REPRESENTS THE FINAL AGREEMENT BETWEEN THE PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES. THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN THE PARTIES.

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EXHIBIT A

SUMMARY OF TERMS AND CONDITIONS

PAR PETROLEUM CORPORATION

$200,000,000 PRIVATE PLACEMENT

Capitalized terms not otherwise defined herein have the same meanings as specified therefor in the

commitment letter (the “Commitment Letter”) to which this Summary of Terms and Conditions is attached.

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