アザクライゼン転位とその周辺 : 発想と展開

概要

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The Ireland-Claisen rearrangement of the enolates of allyl esters, frequently used for the stereocontrolled C-C bond formation, is not suited for the substrate-controlled asymmetric induction. In order to cover the shortcoming, we investigated the thermal rearrangement of amide enolates and found the 1) the enolate derived from N- (2 E) -butenyl-N-butylpropanamide rearranged with excellent internal asymmetric induction (syn : anti= 199 : 1), that 2) the reaction of those containing chiral alkyl groups on the nitrogen proceeded with high selectivity (up to 19 : 1) in relative asymmetric induction, and that 3) the rearrangement can satisfactorily be extended to the acetamides with a heteroatom at the a-position. Utilyzing the reaction, (-) -verrucarinolactone, D-allo-isoleucine, and (-) -isoiridomyrmecin were synthesized with excellent stereoselectivity in short steps. Through the study, an efficinet, mild and versatile method for the hydrolysis of N-monosubstituted carboxamides, and N, N, N′, N′-tetramethylazodicarboxamide (TMAD) -Bu3P, a new reagent system applicable to the Mitsunobu reaction of Brønsted acid of pKα up to 13.5 were developed. The latter provides an efficient general method for the preparation of allylic secondary amines.
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