Grignard reagents react with 4,4,5,5-tetramethyl-1,3,2-dioxaborolane, pinacolborane, under ambient reaction conditions to afford the corresponding pinacolboronate esters.  This reaction is very general, one equivalent of halide (aliphatic, aromatic, heteroaromatic, vinyl or allylic) is transformed into the corresponding Grignard reagent followed by the addition of a single equivalent of pinacolborane in THF.  Iodine also reacts with pinacolborane at ambient reaction conditions in THF to form the iodoalkoxy borate species (4-iodobutoxy)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane. One equivalent of iodine and pinacolborane react to form IBpin, which then interacts with 4-, 5-, or 6-membered cyclic ethers by cleavage of one ether bond to form the corresponding iodoalkoxy pinacolborate.  Treatment with aryl Grignard reagent reacts with one of iodoalkoxy pinacolborate in THF to form the corresponding aryl pinacolboronate ester while reforming and liberating THF as a leaving group.

Preparation and reactions of halobutoxy pinacolborane: Novel synthesis of substituted arylpinacolboronate esters via iodobutoxy pinacolborate utilizing THF as a leaving group

248th National Meeting (2014)

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