摘要:
The action of t-BuOK on alkynyldihalomethanes RC=CCHBrX (I, R = Me, t-Bu, Ph; X = Br, Cl) in pentane at -20 to 0-degrees-C generates the corresponding alkynylhalocarbenes RC=CCX (II; X = Br, Cl) which in the presence of olefins give alkynylhalocyclopropanes (V) in 26-70% yield. It has been shown for the example of the reaction of (methylethynyl-) and (tert-butylethynyl)bromocarbenes with cis-butene-2 that the cycloaddition is fully stereospecific. The selectivity index for (methylethynyl)bromocarbene was experimentally determined as 0.48 which is evident for electrophilic character in this carbene.