Vinylaminodichloroboranes with carbonyl compounds

Aldol condensation. Boron trichloride converts imines into vinylaminodi-chloroboranes, which react at room temperature with carbonyl compounds to form aldols in reasonable yield. An example is shown in equation (I). This aldol condensation can be carried out with comparable yield in a one-pot procedure without isolation of the vinylaminodichloroborane. ... 

Table 3 Directed Aldol Reactions of Vinylaminodichloroboranes (17) with Carbonyl Compounds (Scheme 5)...

An interesting variant of the original reaction discovered by Wittig has been reported in which carbonyl compounds undergo reactions with vinylaminodichloroboranes (17) derived from ketimines to give, upon hydrolytic work-up, the expected aldol adducts (18 Scheme 5). The reactions proceed in fair to good overall yields but with relatively poor diastereoselectivity (Table 3). The extension of this reaction... 

Overall yield based on carbonyl compound for two-step procedure with isolation of intermediate vinylaminodichloroborane. "Isolated yield of aldol adduct according to one-pot procedure. 

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