Chloramine reactions with organoboranes

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). 

The iodine monochloride is an ideal reagent except for the necessity of its handling or preparation. This difficulty has been overcome by the reaction of organoboranes with iodide ion in the presence of mild oxidizing agent chloramine-T 177). The reaction proceeds under extremely mild conditions to afford the corresponding alkenyl iodides (Eq. 115)178) where it can tolerate a variety of functional groups. 

It is well-known that organoboranes can be utilized to yield primary amines by treating them with chloramine or hydroxylamine-O-sulfonic acid Recently Kabalka et al. reported a convenient synthesis of primary alkyl amines via the reaction of organoboranes with ammonium hydroxide in the presence of sodium hypochlorite (Eq. 13) The reaction presumably proceeds through the in situ formation of chloramine. 

Organoboranes react with a mixture of aqueous NH3 and NaOCl to produce primary amines. It is likely that the actual reagent is chloramine NH2CI. Chloramine itself,hydroxylamine-O-sulfonic acid in diglyme, and trimethyl-silyl azide " also give the reaction. Since the boranes can be prepared by the hydroboration of alkenes (15-16), this is an indirect method for the addition of NH3 to a double bond with anti-Markovnikov orientation. Secondary amines can be prepared by the treatment of alkyl- or aryldichloroboranes or dialkylchlorobor-anes with alkyl or aryl azides. 

An analogous reaction is the conversion of olefins into primary amines by the consecutive action of BH3. THF and trimethylsilyl azide171. The observation172 that organoboranes and chloramine give primary amines is the basis of an amine synthesis in which olefins are treated with the complex BH3 THF, followed by aqueous ammonia and aqueous sodium hypochlorite173. Imines are reduced by the chiral dioxaborolidine 162 to yield optically active amines. 1-Imino-l-phenylpropane, for instance, affords 1-phenylpropylamine in 73% enantiomeric excess (equation 59)174. 

Several papers have appeared describing the synthesis of alkyl halides from organoboranes. Alkyl chlorides are obtained by the reaction of trialkylboranes with dichloramine-T, and in somewhat lower yield with iV,N-dichlorourethane/ whereas alkyl bromides are produced in excellent yield when the boranes derived from terminal alkenes and dicyclohexylborane are treated with either Bt2 or BrCl. Alkyl iodides are obtained from the same boranes by the use of ICl-NaQAc " or iodide ion-chloramine-T/ and this latter method has been applied to the radioiodination of olefins (with Vinyl iodides result from... 

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