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Borane-induced ring closure reaction of oligomethylene-linked bis-allenes.

ABSTRACT: The trimethylene-linked bis-allene 3a reacts with Piers' borane [HB(C₆F₅)₂] by a hydroboration/allylboration sequence to generate the cyclization product 5a. Its pyridine adduct was isolated and characterized by X-ray diffraction. Compound 5a undergoes a typical frustrated Lewis pair 1,2-P/B alkene addition reaction with PPh₃ to give the heterobicyclic bridged olefinic zwitterionic product 9a. The tetramethylene-linked bis-allene 3b and its phenylene annulated analogue 3c react with HB(C₆F₅)₂ to give the analogous seven-membered ring products 5b,c under mild conditions. The cyclization product 5a undergoes a series of sequential allylboration reactions with two equivalents of allene followed by ring-closure to give the four-component coupling product 12a. It undergoes FLP addition to an exo-methylene group upon treatment with PPh₃. Compound 12a is oxidatively converted to the boron-free alcohol.

SUBMITTER: Tao X

PROVIDER: S-EPMC8148058 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Borane-induced ring closure reaction of oligomethylene-linked bis-allenes.

Tao Xin X Škoch Karel K Daniliuc Constantin G CG Kehr Gerald G Erker Gerhard G

Chemical science 20191218 6

The trimethylene-linked bis-allene 3a reacts with Piers' borane [HB(C6F5)2] by a hydroboration/allylboration sequence to generate the cyclization product 5a. Its pyridine adduct was isolated and characterized by X-ray diffraction. Compound 5a undergoes a typical frustrated Lewis pair 1,2-P/B alkene addition reaction with PPh3 to give the heterobicyclic bridged olefinic zwitterionic product 9a. The tetramethylene-linked bis-a ...[more]

PMID: 34084385

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