Stereoselective construction of quaternary centers at ambient temperature by the highly stereocontrolled migration of groups containing sp-, sp2-, and sp3-hybridized carbon atoms
摘要:
A very highly diastereoselective semipinacol rearrangement of 2,3-epoxy alcohols mediated by tin(IV) chloride at ambient temperatures is shown to be applicable to a wide variety of migrating groups including methyl, tert-butyl, cyclopropyl, vinyl, alkynyl, phenyl, and 2-furyl. A synthetically valuable feature is that a mixture of syn- and anti-epoxy alcohols affords only a single diastereoisomerically pure beta-hydroxy ketone. Additional advantages of the reaction include the presence in the product of two adjacent stereocenters and the efficient creation of a new quaternary center, valuable features in the synthesis of a variety of natural products.
Zinc bromide as catalyst for the stereoselective construction of quaternary carbon: improved synthesis of diastereomerically enriched spirocyclic diols
作者:Yong Qiang Tu、Chun An Fan、Shi Kuo Ren、Albert S. C. Chan
DOI:10.1039/b006182o
日期:——
proved to be a facile and efficient catalyst for the stereoselective semipinacol rearrangement of α-hydroxy epoxides at room temperature. Of note are the presence in the product of two adjacent chiral carbon centers, particularly the creation of a stereoselective quaternary center, and the efficient synthesis of β-hydroxy ketones, including some with naturally occurring spiroalkane skeletons. As an