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Diastereoselective synthesis of CF₃-dihydrobenzofurans by [4+1] annulation of in situ-generated CF₃-o-quinone methides and sulfur ylides.

ABSTRACT: An efficient and highly diastereoselective synthesis of CF₃-dihydrobenzofurans by the reaction of in situ-generated CF₃-oQMs in the presence of a base with sulphur ylides is put forward. The generality of the present developed method was well studied with diverse substrates to access the corresponding products in excellent yields. The highly reactive CF₃-oQM has been utilized first time for the annulation reaction.

SUBMITTER: Jha BK

PROVIDER: S-EPMC9057278 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Diastereoselective synthesis of CF3-dihydrobenzofurans by [4+1] annulation of in situ-generated CF3-o-quinone methides and sulfur ylides.

Jha Babli K BK Prudhviraj Jaggaraju J Mainkar Prathama S PS Punna Nagender N Chandrasekhar Srivari S

RSC advances 20201020 63

An efficient and highly diastereoselective synthesis of CF3-dihydrobenzofurans by the reaction of in situ-generated CF3-oQMs in the presence of a base with sulphur ylides is put forward. The generality of the present developed method was well studied with diverse substrates to access the corresponding products in excellent yields. The highly reactive CF3-oQM has been utilized first time for the annulation reaction. ...[more]

PMID: 35517513

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Project description:CONSPECTUS: An ortho-quinone methide (o-QM) is a highly reactive chemical motif harnessed by nature for a variety of purposes. Given its extraordinary reactivity and biological importance, it is surprising how few applications within organic synthesis exist. We speculate that their widespread use has been slowed by the complications that surround the preparation of their precursors, the harsh generation methods, and the omission of this stratagem from computer databases due to its ephemeral nature. About a decade ago, we discovered a mild anionic triggering procedure to generate transitory o-QMs at low temperature from readily available salicylaldehydes, particularly OBoc derivatives. This novel reaction cascade included both the o-QM formation and the subsequent consumption reaction. The overall transformation was initiated by the addition of the organometallic reagent, usually a Grignard reagent, which resulted in the formation of a benzyloxy alkoxide. Boc migration from the neighboring phenol produced a magnesium phenoxide that we supposed underwent β-elimination of the transferred Boc residue to form an o-QM for immediate further reactions. Moreover, the cascade proved controllable through careful manipulation of metallic and temperature levers so that it could be paused, stopped, or restarted at various intermediates and stages. This new level of domestication enabled us to deploy o-QMs for the first time in a range of applications including diastereocontrolled reactions. This sequence ultimately could be performed in either multipot or single pot processes. The subsequent reaction of the fleeting o-QM intermediates included the 1,4-conjugate additions that led to unbranched or branched ortho-alkyl substituted phenols and Diels-Alder reactions that provided 4-unsubstituted or 4-substituted benzopyrans and chroman ketals. The latter cycloadducts were obtained for the first time with outstanding diastereocontrol. In addition, the steric effects of the newly created stereocenters in subsequent reactions of chroman ketals and acetals were studied and proved predictable. Through the use of a chiral auxiliary, Diels-Alder products were deployed in numerous enantioselective reactions including several complex natural products syntheses. In this Account, we summarize our efforts, which we hope have contributed to the synthetic renaissance for this venerable species.

Dataset Information

Diastereoselective synthesis of CF₃-dihydrobenzofurans by [4+1] annulation of in situ-generated CF₃-o-quinone methides and sulfur ylides.

Publications

Diastereoselective synthesis of CF<sub>3</sub>-dihydrobenzofurans by [4+1] annulation of <i>in situ</i>-generated CF<sub>3</sub>-<i>o</i>-quinone methides and sulfur ylides.

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