112142-87-7Relevant academic research and scientific papers
Azirine/oxindole ring enlargement via amidinium intermediates
Mekhael, Maged K. G.,Bienz, Stefan,Linden, Anthony,Heimgartner, Heinz
, p. 2385 - 2404 (2007/10/03)
A novel general method for the synthesis of oxindoles, namely the 'azirine/oxindole ring enlargement via amidinium-intermediates' has been established: the reaction of 2H-azirin-3-amines 1 with BF3· OEt2 in THF solution at -78° leads
Diazo-Transfer Reaction with Diphenyl Phosphorazidate
Villalgordo, Jose M.,Enderli, Adelheid,Linden, Anthony,Heimgartner, Heinz
, p. 1983 - 1998 (2007/10/02)
Diphenyl phosphorazidate (DPPA) was used as the azide source in a one-pot synthesis of 2,2-disubstituted 3-amino-2H-azirines 1 (Scheme 1).The reaction with lithium enolates of amides of type 2, bearing two substituents at C(2), proceeded smoothly in THF at 0 degree C; keteniminium azides C and azidoenamines D are likely intermediates.Under analogous reaction conditions, DPPA and amides of type 3 with only one substituent at C(2) gave 2-diazoamides 5 in fair-to-good yield (Scheme 2).The corresponding 2-diazo derivatives 6-8 were formed in low yield by treatment of the lithium enolates of N,N-dimethyl-2-phenylacetamide, methyl 2-phenylacetate, and benzyl phenyl ketone, respectively, with DPPA.Thermolysis of 2-diazo-N-methyl-N-phenylcarboxamides 5a and 5b yielded 3-subdtituted 1,3-dihydro-N-methyl-2H-indol-2-ones 9a and 9b, respectively (Scheme 3).The diazo compounds 5-8 reacted with 1,3-thiazole-5(4H)-thiones 10 and thiobenzophenone (13) to give 6-oxa-1,9-dithia-3-azaspironona-2,7-dienes 11 (Scheme 4) and thiirane-2-carboxylic acid derivatives 14 (Scheme 5), respectively.In analogy to previously described reactions, a mechanism via 1,3-dipolar cycloaddition, leading to 2,5-dihydro-1,3,4-thiadiazoles, and elimination of N2 to give the 'thiocarbonyl ylides' of type H or K is proposed.These dipolar intermediates with a conjugated C=O group then undergo either a 1,5-dipolar electrocyclization to give spiroheterocycles 11 or a 1,3-dipolar electrocyclization to thiiranes 14.
