Alkylations 9-borabicyclo nonane dimer

In contrast to trialkylboranes BR3, the mono- and dialkylboranes R2BH and RBH2 are dimers with structures related to diborane(6) i.e., they are alkyldiboranes. With a few exceptions (borolane dimers and 9-borabicyclo[3.3.1]nonane dimer) they may also be in equilibrium at room temperature with small amounts of monomer. Characteristically there is rapid R/H exchange. Hence alkyldiboranes are in most cases mixtures of boranes in various degrees of alkylation. Tetraalkyldiboranes are therefore mixtures of alkyldiboranes and trialkylboranes, and the mixtures have mean compositions corresponding to a tetraalkylated diborane ... 

The reaction of alkyl derivatives of 9-borabicyclo [3.3.1]nonane dimer (9-BBN) with (1) results in migration of the. S-cyclooctyl group, producing A(-Boc-5-aminocyclooctanol... 

Borabicyclo[3.3.1]nonane (9-BBN) has found use in the selective hydro-boration of alkenes in the presence of other reducible functional groups and its reaction with alkynylstannates has been studied. o-Stannyl- and a-silyl-substituted crotyl-9-BBN show promise as reagents for the stereo-regulated synthesis of acyclic systems. A series of papers covers the question of olefin-alkyl exchange in. 5-alkyl-9-BBN s, " the kinetics of reduction of substituted benzaldehydes with 9-BBN, and the kinetics and mechanism of hydroboration of alkynes with 9-BBN dimers. Selective dehalogenation of tertiary alkyl, benzyl, and allyl halides in the presence of secondary or primary alkyl or aryl halides is possible with (165). The... 

Koster [1] was the first to report the preparation, isolation, and characterization of 9-borabicyclo[3.3.1]nonane as a dimer (9-BBN)2 has been obtained from the thermal disproportionation of tetra-n-propyldiborane and B-n-propyl-9-BBN (Eq. 3.1). B-alkyl-9-BBN preparation is itself a two-step process, thus restricting the utility of the 9-BBN for synthetic purposes. 

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