Weinreb Amide Introduction
来源:    发布时间: 2014-02-01 00:00   3675 次浏览   大小:  16px  14px  12px

The standard conditions for the Weinreb–Nahm ketone synthesis are known to tolerate a wide variety of functional groups elsewhere in the molecule, including alpha-halogen substitution, N-protected amino acids, α-β unsaturation, silyl ethers, various lactams and lactones, sulfonates, sulfinates, and phosphonate esters. A wide variety of nucleophiles can be used in conjunction with the amide. Lithiates and Grignard reagents are most commonly employed; examples involving aliphatic, vinyl, aryl, and alkynyl carbon nucleophiles have been reported. However, with highly basic or sterically hindered nucleophiles, elimination of the methoxide moiety to release formaldehyde can occur as a significant side reaction.

Nonetheless, the Weinreb–Nahm amide figures prominently into many syntheses, serving as an important coupling partner for various fragments. Shown below are key steps involving Weinreb amides in the synthesis of several natural products, including members of the immunosuppressant family of Macrosphelides, and the antibiotic family of Spirofungins.

 

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