Chemoselective Cross Metathesis of Bishomoallylic Alcohols: Rapid Access to Fragment A of the Cryptophycins
摘要:
The racemic or enantioselective allylation of in situ formed beta,gamma-unsaturated aldehydes provides efficient access to bishomoallylic alcohols from readily available 2-vinyloxiranes. These products, when subjected to modified Grubbs cross metathesis conditions, afforded terminally homologated products in moderate to good yields with high E selectivity and without degradation of the enantiomeric excess. The compounds obtained through this two-step sequence yield fragments of an important and pharmacologically active family of cryptophycins.
Contemporaneous Dual Catalysis: Aldol Products from Non‐Carbonyl Substrates
作者:Barry M. Trost、Jacob S. Tracy
DOI:10.1002/chem.201502973
日期:2015.10.19
carbon–carbon bond‐forming reactions vital to modern organic synthesis. Despite the attention this reaction has received, issues related to chemo‐ and regioselectivity as well as reactivity of readily enolizable electrophiles remain. To help overcome these limitations, a new direct approach toward aldol products that does not rely upon carbonyl substrates is described. This approach employs room‐temperature
Preparation of Homoallylic Homopropargylic Alcohols from 2-Vinyloxiranes
作者:Matthew L. Maddess、Mark Lautens
DOI:10.1021/ol051326l
日期:2005.8.1
beta, gamma-Unsaturated aldehydes generated in situ by treatment of 2-vinyloxiranes with a catalytic amount of Sc(OTf)3 or (BFOEt2)-O-. are effectively trapped by B-allenyl-9-BBN to afford homoallylic homopropargylic alcohols in high yield. An enantioselective version has been demonstrated, and a convenient synthesis of 9-allenyl-9-BBN is described.