Diboration of 1,3-diene

Diborations of 1,3-dienes are carried out in the presence of platinum(O) catalyst. In the Pt(PPh3)4-catalyzed dibora-tion of 1,3-dienes, 1,4-addition takes place to give (Z)-l,4-diboryl-2-alkenes stereoselectively (Equation (10)).62 In contrast, the Pt(dba)2-catalyzed reaction of 1,3-pentadiene affords 1,2-addition product, in which more substituted C=C bond is left intact (Scheme 5). The use of Pt(dba)2 as catalyst also enables the diborative dimerization of isoprene to occur (Equation (ll)).48... 

The last cascade reaction we report here for the synthesis of a quaternary spirocenter employs a platinum catalyst [21 ]. A regio and enantioselective diboration of 1,3-diene 44 could lead to a chiral bis(boryl) intermediates 45 (Scheme 9.12), which could then react in two subsequent asymmetric carbonyl allylations of succinic dialdehyde, leading to the creation of three stereogenic centers in good diastereomeric (9 1) and promising enantiomeric ratios (88 12) 46. 

Diboration of 1,3-Dienes, Allenes, Enones, and Other Unsaturated Molecules. As described previously in the original article, the Pt[0] catalyzed addition of 1,3-dienes with B2pin2 affords various allylboronic esters (eq 4). Reactions using phosphine-based catalysts such as Pt(PPh3)4 stereoselectively produce els -1,4-addition products with Z-configuration for aliphatic and cyclic dienes. The reaction mechanism suggests... 

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