RESUMO
Chiral 2,3-allenols were constructed through copper(I)-catalyzed asymmetric direct alkynylogous aldol reaction. With aromatic and heteroaromatic aldehydes, the alkynylogous aldol reaction with (R)-DTBM-SEGPHOS as the ligand proceeded smoothly to furnish the products in excellent regioselectivity with good to high diastereoselectivity and excellent enantioselectivity. In the cases of aliphatic aldehydes, esters of but-2-yn-1-ol as the substrates and (R,R)-Ph-BPE as the ligand were found to be crucial to get good to high regio- and diastereoselectivity. The produced chiral 2,3-allenols are easily transformed into synthetically useful 2-furanones through cyclization. Finally, the developed method was successfully applied in the rapid synthesis of two chiral intermediates toward the synthesis of two pharmaceutically active compounds that have been proposed for the treatment of neurological disorders.
RESUMO
A copper-catalyzed silylation of propargyl dichlorides was developed to access chloro-substituted allenylsilanes under mild reaction conditions. Moreover, enantioenriched chloro-substituted allenylsilanes can be synthesized in moderate to high yields and good enantioselectivities with this protocol.
RESUMO
Copper-catalyzed divergent conjugate protosilylation and protoborylation of polar enynes were developed. The corresponding ß-boryldienoates and ß-silyldienotes were obtained in moderate to good yields and with good stereoselectivity. In this protocol, novel cascade double protoborylation/protodeboronation processes of polar enynoates enabled access of the useful trisubstituted vinylboronates in up to 80% yield and with up to 98:2 Z/ E ratio. Moreover, divergent transformations of the products thus obtained were also investigated.
