Asymmetric hetero-Diels–Alder reactions of alkenyldihydrooxazoles. Synthesis of oxazolo[3,2-c]pyrimidines and related compounds
作者:Mark C. Elliott、Elbertus Kruiswijk
DOI:10.1039/a905700e
日期:——
Alkenyldihydrooxazoles undergo a highly diastereoselective formal aza-Diels–Alder reaction with aryl and arenesulfonyl isocyanates to give oxazolo[3,2-c]pyrimidines. Depending on the substitution pattern of the alkenyldihydrooxazole, these compounds may then undergo addition of a second equivalent of the isocyanate to give either tetrahydrooxazolo[3,2-c]pyrimidine-8-carboxamides or octahydroazeto[2
烯基二氢恶唑与芳基和芳烃磺酰基异氰酸酯进行高度非对映选择性的正式aza-Diels-Alder反应,生成oxazolo [3,2- c ]嘧啶。然后,根据烯基二氢恶唑的取代方式,可以将这些化合物加入第二当量的异氰酸酯,以得到四氢恶唑并[ 3,2 - c ]嘧啶-8-羧酰胺或八氢氮杂并[2,3- d ]恶唑[3]。 ,2- c ]嘧啶。第二种添加对空间和电子因素敏感,在某些情况下可以防止。
Alternative synthesis of α-substituted β-amidophosphines by [1,4]-addition. A new route to chiral ligands
Phosphine-borane can be diastereoselectively added to chiral alpha,beta-unsaturated amides 3, using amino-alcohols as chiral inducers, leading to alpha-substituted beta-amidophosphine boranes 4 with up to 74% diastereomeric excess. Selective deprotection afforded optically pure carboxylic derivatives 5 which are key intermediates for the synthesis of various potential chiral ligands for asymmetric catalysis. (C) 2002 Published by Elsevier Science Ltd.
Diastereoselective Synthesis of Chiral Amidophosphonates by 1,5-Asymmetric Induction
We have investigated two simple diastereoselective syntheses of substituted β-amidophosphonates. The first one involved a Michael addition to α,β-unsaturated amides 6 and 8a−d, derived fromchiral amino alcohols, and permitted the preparation of alkyl-substituted derivatives 7 and 9a−d with high diastereoselectivities (up to 95%) with the aid of a 1,5-asymmetric induction. The second one, involving
Highly diastereoselective hetero-Diels–Alder reactions of alkenyldihydrooxazoles as an approach to novel pyrimidine derivatives
作者:Mark C. Elliott、Elbertus Kruiswijk
DOI:10.1039/a705571d
日期:——
Chiral 2-alkenyldihydrooxazoles react with two equivalents of aryl and arylsulfonyl isocyanates to give chiral nonracemic dihydropyrimidone derivatives in high yield and with complete diastereocontrol.