Computational studies hydroboration

Computational studies of both hydroalumination and carboalumination have indicated a four-center TS for the addition.220 The aluminum reagents, however, have more nucleophilic character than do boranes. Whereas the TS for hydroboration is primarily electrophilic and resembles that for attack of CH3+ on a double bond, the... 

One computational study see Molecular Orbital Theory) has appeared using RhCl(PH3)2 to model the rhodium-catalyzed hydroboration of ethylene see Hydroboration Catalysis). Both associative and dissociative pathways were examined (equation 47). In the associative path, three possible... 

Quinazolinap ligand. Smith and Takacs reported an efficient amide directed asymmetric hydroboration of trisubstituted alkenes using TADDOL-deffved phenyl monophosphite ligands. Demay et reported the hydroboration reaction using C2-symmetric 1,2-diphosphane ligands. Evans and Fu suggested a catalytic cycle for catalytic hydroboration, which was supported by computational studies. ... 

Computational studies of the formation of ( )-5-stannyl homoallylic alcohols by an allene hydroboration-aldehyde allylboration sequence show that the kinetic allene hydroboration product is less stable and isomerizes to the more sterically congested a-stannylallylborane with the C—Sn to boron a—n hyperconjugation interaction sufficiently stabilizing to override the steric congestion (Scheme 77). " ... 

Hydroboration of carbonyl compounds by pinacolborane is chemoselectively catalysed by titanocene bis(catecholborane) (A). Aryl aldehydes and ketones produce alkoxypinacolboronate esters (B) in moderate to high yields. The facile hydrolysis of B over silica affords alcohols in good yields. The catalytic hydroboration of electron-poor acetophenones is faster than that for electron-rich acetophenones. Computational studies with benzophenone and benzaldehyde indicated that hydroboration is spontaneous and probably proceeds via Ti metallacycle intermediates whose structures... 

A general approach to the hydrogenation of alkynes to cw-alkenes under mild conditions using the ansa-aminohydroborane (2-[bis(pentafluorophenyl)boryl]-A, A-dimethylaniline) (77) as a catalyst. The approach combines several reactions as the elementary steps of the catalytic cycle hydroboration (substrate binding), heterolytic hydrogen splitting (typical frustrated Lewis-pair reactivity) and facile intramolecular protodeborylation (product release). The mechanism is verified by experimental and computational studies." ... 

Deviation from the anti-Markovnikov rule a computational study of the regio- and stereoselectivity of diene hydroboration reactions... 

Computations show that an H2 complex lies along the reaction coordinate, and W(H2)(CO)5 may also be an intermediate in W(CO)6-catalyzed reactions.7 Examples of the significance of a complexes in industrial and biological processes will be discussed below as well as in Chapter 10. Theoretical studies of a variety of hydrogenations and hydroborations have been reviewed by Frenking, and ff-com-plex intermediates are often identified along the reaction coordinate. 

We characterized the specificity of the direct hydroboration reaction products of straight chain and cyclic dienes using computational methods. It was previously thought that only partial hydroboration takes place in dienes, resulting in unsaturated reaction products described by Brown and Bhat [18]. Our recent study [17] demonstrated that hydroboration was not limited to one of the double bonds, and that in fact polymers formed as a result of fiiUy saturated, boron-containing hydrocarbons cross-linking... 

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