Diastereoselective Copper-Mediated Cross-Couplings between Stereodefined Secondary Alkylcoppers with Bromoalkynes
摘要:
A copper(I)-mediated cross-coupling of stereo defined secondary alkyllithiums with bromoalkynes provided stereodefined alkynes with high diastereoselectivity (dr up to 98:2). This cross-coupling was extended to various secondary alkyllithiums bearing a remote oxygen functionality, and the alkyne synthesis was also performed with optically enriched alkyl iodides (up to 99% ee) providing, after cross-coupling, alkynes bearing two stereocenters (dr = 93:7; up to 99% ee).
A general and efficient Cu(I)-catalyzed cross-coupling reaction of alkynyl bromides and β-tributylstannyl-α,β-unsaturated ester bearing a trifluoromethyl group in β-position was developed under very mild conditions. This method provides easy access to a variety of 2,3-enynoate bearing a trifluoromethyl group from good to excellent yields with excellent stereoselectivity. This procedure does not require
E-conjugated enynes bearing an acetal function on the allylic or the homoallylic position or/and on the propargylic or the homopropargylic position were conveniently obtained at room temperature in DMF via cross coupling of the corresponding vinyltins with 1-bromoalk-1-ynes in the or Pd(II) catalysts.