Allenyl halides, reactions with Grignard reagents

In the early 1980s, one of the first preparations of substituted allenes was reported, which employed a palladium-catalyzed cross-coupling reaction of allenyl halides [9]. In this study, allenyl bromides 13 and various Grignard reagents 14 were coupled in the presence of catalytic amounts of a Pd(0) species, generated in situ by reduction of a Pd(II) salt. Trisubstituted allenes 15 were obtained with high regioselectivity (allene 15 alkyne 16 = 90 10 to 99 1) (Scheme 14.5). 

Allenylstannanes can be prepared by the reaction of allenyl Grignard reagents with tin halides (equation 9-36), or of stannylmetallic reagents (e.g. R3SnLi, R3SnCu) with propargyl halides or sulfonates (equation 9-37) 88,89 reactions of this latter type occur with complete inversion of structure. 

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