Allylboronates from Homologation of Alkenylboronates

Alkenylboronates can be converted into functionalized allylboronates such as 42 by way of a Matteson homologation (Equation 24) [63-65]. This strategy is the reverse of the addition of alkenylmetal intermediates to halomethylboronates described in Section 6.2.1.2. It is an attractive method because the requisite alkenylboronates are readily prepared by the hydroboration of terminal alkynes. Differentially substituted 3,3-dialkyl allylboronates, a class of reagents that would be difficult to access otherwise, were synthesized using this route [66]. The use of Cl2CHLi as reagent in this method 

Brown and co-workers employed a related three-carbon variant of the Matteson homologation chemistry to access a-alkyl- and a-aryl allylboronates such as 44 from chloroallylic carbanion 43 (Equation 25) [69]. 

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