Nafion-H-catalyzed Mukaiyama aldol condensations and hetero Diels–Alder reactions using aldehydes and imines. Part 15: General synthetic methods
摘要:
Nafion-H catalyzes the Mukaiyama aldol condensation between aromatic aldehydes and the Danishefsky diene whereas the corresponding imines directly undergo hetero Diels-Alder cyclization to form 2,3-dihydro-gamma -pyridones. Some chiral acetal derived aldehydes were round to undergo Mukaiyama aldol condensation in the presence of Lewis acids but not with Nafion-H. (C) 2001 Elsevier Science Ltd. All rights reserved.
A lithium methoxide-catalyzed hetero Diels–Alder reaction of aromatic and aliphatic aldehydes with 1-methoxy-3-trimethylsilyloxy-1,3-butadiene (Danishefsky’s diene) is described. It proceeds through the Mukaiyama-Aldol reaction pathway and affords the corresponding 2,3-dihydropyran-4-one skeletons in good to excellent yields.
A novel Ce(III)–(R)-BNP complex was conveniently prepared from CAN and (R)-BNP–Na, then successfully used as a homogeneous catalyst for the asymmetric hetero-Diels–Alder reaction affording, after acidic work-up, 6-substituted 5,6-dihydro-4H-pyran-4-one derivatives with high enantioselectivities (up to 94% ee). A mechanistically interesting positive nonlinear effect was also observed.
Control of selectivity in the generation and reactions of oxonium ylides
作者:Deana M. Jaber、Ryan N. Burgin、Matthew Hepler、Peter Zavalij、Michael P. Doyle
DOI:10.1039/c1cc12443a
日期:——
Dirhodium catalyzed reactions of aryl-substituted tetrahydropyranone diazoacetoacetates produce ylide intermediates that unexpectedly yield two oxabicyclo[4.2.1]-nonane diastereoisomers, but a single diastereoisomer is formed by increasing the steric bulk of the aryl substituent.
A palladium(ii)-catalyzed direct alkenylation reaction of dihydropyranones was developed.
开发了一种钯催化的直接烯丙基化反应,用于二氢吡喃酮。
Hetero Diels-Alder Type Reactions Between Danishefsky’s Dienes in the Presence of Lewis Base Catalysts. An Efficient Method for the Synthesis of Substituted 2,3-Dihydropyran-4-ones