University of Leicester
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Dialkylphosphinic-N, N-dichloroamides and related azides.

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posted on 2015-11-19, 08:47 authored by Michael Alexander. Stephen
Azido, N-chloroainino, and N,N-dichloroamino derivatives of dialkyl- phosphinic acids have been synthesised. The azides upon photolysis in alcohols (except isopropanol) or t-butylamine give products derived from alkyl migration from phosphorus to nitrogen with incorporation of a molecule of solvent. Diisopropyl and di-t-butylphosphinic azides also give amides and products derived from insertion of a formal nitrene into the O-H bond of the alcohol. Diethylphosphinic azide undergoes predominantly nucleophilic substitution by the methanol solvent. Anhydrides formed in the photolysis of di-t-butylphosphinic azide in cyclohexane and benzene arise from the presence of adventitious moisture and accompany nitrene products. The formation of these products is discussed in terms of independent routes involving either a metaphosphonimidate intermediate (only trapped in protic solvents) or a singlet nitrene that decays to a triplet nitrene. An equilibrium has been shown to exist between amides, N-chloro- amides, and N,N-dichloroamides. The chloroamides add to phenylethylenes to yield anti-Markovnikov products after reduction, these cyclise with base to aziridines. The formation of cis and trans adducts in the reaction of t-1-(N-chloro-N-methylamino)-2,2,r-3,4,4-pentamethylphos- phetan-l-oxide with styrene is discussed in terms of a pseudorotation mecliaiiism. The initial N-chloro adduct has been isolated in the reaction of (N,N-dichloro)di-t-butylphosphinic amide with styrene. Attempts to form ring expanded products in the reaction of t-1-(N-chloroamino) - and t-1- (N,N-dichloroamino)-2,2,r-3,4,4-pentamethylphos- phetan-l-oxides (141) and (140) respectively yielded only the parent amide. The formation of an anionic species in these reactions was shown by trapping with methyl iodide. The N-chloroamides with anthracene give 9-chloro and 9,10-dichloro- anthracenes. The o:m:p ratio of chloroanisoles formed in the reaction of the chloroamides (140) and (141) is used to elucidate the nature of the mechanism of the chlorination reactions. Triphenylarsine has been tried as a trap for nitrenes generated from N,N-dichloroamides and azides, without success.


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University of Leicester

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  • Doctoral

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  • PhD



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