Amines synthesis using organoboranes

Sulfonylhydroxylamines and hydroxylamine O-sulfonic acid have found wide apph-cation in synthesis of amines from achiral or chiral organoboranes and boronate esters and the hydroboration-amination methodology is successfully used for direct amination of alkenes. 0-Sulfonyloximes were also found to be good reagents for synthesis of amines from organomagnesium, -copper and -zinc reagents. 

The reaction of trialkylboranes with iV-chloroalkylamines can be used to synthesize a wide variety of functionally substituted dialkylamines in good yields [66,67], and it complements the synthesis of secondary amines via the reaction of trialkylboranes with organic azides. The reaction is analogous to the reaction of chloramine with organoboranes, and presumably occurs via an anionotropic migration of an alkyl group from boron to nitrogen (Scheme 24). 

Synthesis of pure enantiomers. Brown and Singaram1 have reviewed the chiral organoboranes obtained from (+)- and (- )-pinene and their use for synthesis of optically pure amines, halides, hydrocarbons, lithium alkylborohydrides, ketones, aldehydes, a-chiral acids, esters, nitriles, alkynes, and alkenes. 

Organoboranes possessing one B—C bond in the molecule can also be obtained by hydroborating alkenes and alkynes with heterosubstituted borane derivatives, especially dihalogenoboranes, which can be stabilized by complexation with amines, phosphines, ethers and sulfides. The last two are useful complexing agents for both the preparation and the reactions of dihalogenoboranes . The most convenient synthesis of dichloroborane etherate is the reaction of LiBH. with BCl, in Et,0 ... 

Organoboranes can be used for the synthesis of various organic compounds containing an amino group . The most common procedures involve the reaction of organoboranes with azides, with hydroxylamine derivatives, or with chloroamines. All amination reactions proceed via intermediate formation of a borate complex followed by anionotropic rearrangement to form the new C—N bond (Equation (21)). 

A little used synthesis of primary alkylamines is the amination of organoboranes. Organoboranes have now been shown to react with chloramine-T prepared in situ from ammonium hydroxide and sodium hypochlorite to give the corresponding amines (Scheme 5). This procedure then represents a mild, one-pot synthesis of various primary alkylamines from alkenes. 

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