85809-30-9Relevant academic research and scientific papers
Three positional isomers of substituted triphenylmethanes from reactions of trityl anion with 1-acyl-2,2-dimethylaziridines
Werry, Juergen,Lin, Pen-Yuan,Assithianakis, Petros,Stamm, Helmut
, p. 3103 - 3110 (2007/10/03)
Ring opening of aziridines 4a-d in reactions with trityl anion Tr(-) proceeds exclusively by cleavage of the NCMe2 bond.Substitution of the benzylic carbon of Tr(-) leads to 'central' products 10a-d in yields of 0-5percent.This is ascribed to an SN2 reaction with borderline character, as is well known from reactions of aziridines 4a-d with other nucleophiles.All remaining ring-opening reactions result from single-electron transfer (SET).This is direct SET from Tr(-) to aziridines 4a-c.For compound 4d (acyl = cinnamoyl), the SET reaction is of the innersphere type and proceeds via Michael addition, at least in part.Homolytic ring opening of the generated aziridino ketyls 5 forms the tertiary amidatoalkyl radicals 6.Main reaction of radicals 6a-c is transfer of a hydrogen atom from one of its two methyl groups to the generated trityl radical Tr..Methallylamides 7 and enamides 8 are the final products. ortho-Substituted triphenylmethanes 12 and/or its olefinic precursors 13 arise in ca. 20percent yield.A mechanism for the formation of these unique products is proposed that first converts the radicals 6 into the corresponding carbanions 16 which undergo an SN2' reaction with one allylic system TrCHCH=CH* of the dimer 14 of Tr..The leaving group Tr(-) is eliminated from this partial structure when carbanions 16 attack the marked carbon converting it finally into the substituted ortho carbon of compounds 12.Addition of radicals 6 to Tr(-) is probably the way to the para-substituted triphenylmethanes 11, which arise in yields of only 0-1percent from aziridines 4a,b (acyl = benzoyl, pivaloyl).Higher yields of para-substituted compounds 11 are obtained from aziridines 4c (acyl = 4-phenylbenzoyl) and 4d.This is ascribed, at least for substrate 4c, to a chain reaction because ketyl 5c must be formed more rapidly than ketyls 5a,b.A substantial part of radical 6d cyclizes, ending up as the triphenylmethane compound 26 that carries a pyrrolidone ring in the para position.
NUCLEOPHILIC CLEAVAGE OF 2,2-DIMETHYLAZIRIDINES: COMPETITION BETWEEN SN2 AND POSTULATED "SET" MECHANISM.
Stamm, H.,Assithianakis, P.,Buchholz, B.,Weiss, R.
, p. 5021 - 5024 (2007/10/02)
Regioselectivity of nucleophilic attack on 2,2-dimethylaziridines depends on the degree of leaving group activation: in highly activated aziridines it occures at the methylene carbon and in less activated at the tertiary carbon.This latter abnormal ring opening is explained by an SET mechanism.
