TY - JOUR
T1 - [2+2] versus [4+2] cycloaddition reactions of 1,3-diaza-1,3-butadienes with various mono- and disubstituted ketenes and supporting mechanistic considerations
AU - Mukherjee, Sucharita
AU - Mazumdar, Sujit N.
AU - Sharma, Arun K.
AU - Mahajan, Mohinder P.
PY - 1998
Y1 - 1998
N2 - Reactions of 1,3-diaza-1,3-butadienes with various mono- and disubstituted ketenes alongwith the associated interesting mechanistic features involved are reported. Reactions of 1,3-diazabutadienes with monosubstituted ketenes e.g. cyano-, p-nitrophenyl-, succinimido-, phthalimido- and phenoxyketenes gave [4+2] cycloadducts irrespective of the nature of azadiene and/or ketene substituents. However, diphenylketene underwent [2+2] cycloaddition reactions with 1,3-diazabutadienes (la) and gave [4+2] adducts with 1b, having electron donating function at 2-position. Interestingly, the reactions of 4-(N-arylamino)-1,3-diaza-1,3-butadienes (19) with diphenylketene gave simple nucleophilic addition products (22), whereas, their reaction with dimethylketene, yielded [4+2] cycloadducts (23). The factors influencing [2+2] versus [4+2] and cyclic versus acyclic products are also discussed.
AB - Reactions of 1,3-diaza-1,3-butadienes with various mono- and disubstituted ketenes alongwith the associated interesting mechanistic features involved are reported. Reactions of 1,3-diazabutadienes with monosubstituted ketenes e.g. cyano-, p-nitrophenyl-, succinimido-, phthalimido- and phenoxyketenes gave [4+2] cycloadducts irrespective of the nature of azadiene and/or ketene substituents. However, diphenylketene underwent [2+2] cycloaddition reactions with 1,3-diazabutadienes (la) and gave [4+2] adducts with 1b, having electron donating function at 2-position. Interestingly, the reactions of 4-(N-arylamino)-1,3-diaza-1,3-butadienes (19) with diphenylketene gave simple nucleophilic addition products (22), whereas, their reaction with dimethylketene, yielded [4+2] cycloadducts (23). The factors influencing [2+2] versus [4+2] and cyclic versus acyclic products are also discussed.
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U2 - 10.3987/com-97-s(n)103
DO - 10.3987/com-97-s(n)103
M3 - Article
AN - SCOPUS:0000936393
SN - 0385-5414
VL - 47
SP - 933
EP - 950
JO - Heterocycles
JF - Heterocycles
IS - 2
ER -