Organoboron compounds rearrangements

Secondary amines have been prepared from organoboron compounds R1315, R12 BC1 or R1BCI2 (R1 = Et, Bu, /-Bu,, v-Bu, 3-hexyl, cyclopentyl etc.) by treatment with azides R2N3 (R2 = Bu, /-Bu, i-Bu, cyclohexyl, Ph etc.) and aqueous work-up. It is suggested that the reactions proceed by way of anionotropic rearrangements (equation 61)176. 

Trialkylboranes add to propellane to give a zwitterion that can rearrange to give 60 or react with another molecule of la to give 61. Both organoboron compounds were oxidized with hydrogen peroxide and isolated as the corresponding alcohols in 65% and 21% yield, respectively (equation 23). 

Applications of Organoborates. Electrophile-induced rearrangements of four coordinate borate salts now provide a major proportion of the new synthetic applications of organoboron compounds. Many of these procedures utilize trialkylal-kynylborates, the basic reaction of which is outlined in reaction (6),... 

Hydrozirconation of alkenes. This organic metallic reagent reacts with olefins at 25-40° to form alkylzirconium complexes of the type (C5115)2 Zn(R)Cl, in which the transition metal moiety is attached to the least hindered position of the olefin. For example, when a suspension of (1) in benzene is shaken with 1-octene or either cis- or tran -4-octene, (2) is formed in quantitative yield. Thus internally metalated zirconium compounds undergo rearrangement much more rapidly than organoboron or aluminum analogs. Other examples of hydrozircon-ation are formulated. Very hindered olefins e.g., tetramethylethylene) fail to react at 40°. 

An unusual (although scarcely preparative) variation of using nitrile 647 for the synthesis of quinazolines was described in late 1970s [396]. Compound 647 reacted with organoboron derivatives to give bora-heterocycles 655, which upon hydrolysis rearranged to quinazoline derivatives 656 (Scheme 135). 

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