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Reaction of cyclic imidates with α,β‐unsaturated esters: Synthesis of new pyrrolo[2,1‐ b ]‐1,3‐oxazine and pyrido[2,1‐ b ]‐1,3‐oxazine derivatives
Author(s) -
Ihara Shogo,
Soma Takashi,
Yano Daigo,
Aikawa Shunichi,
Yoshida Yasuhiko
Publication year - 2011
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.539
Subject(s) - chemistry , dimethyl acetylenedicarboxylate , annulation , cycloaddition , tautomer , methanol , stereochemistry , malonate , bicyclic molecule , medicinal chemistry , organic chemistry , catalysis
Abstract The cycloaddition reaction of cyclic imidates, 2‐benzyl‐5,6‐dihydro‐4 H ‐1,3‐oxazines 1a , 1b , 1c , 1d , 1e , 1f , with dimethyl acetylenedicarboxylate 2 , trimethyl ethylenetricarboxylate 4 , or dimethyl 2‐(methoxymethylene)malonate 6 afforded new fused heterocyclic compounds, such as methyl (6‐oxo‐3,4‐dihydro‐2 H ‐pyrrolo[2,1‐ b ]‐1,3‐oxazin‐7‐ylidene)acetates 3a , 3b , 3c , 3d , 3e , 3f (71–79%), dimethyl 2‐(6‐oxo‐3,4,6,7‐tetrahydro‐2 H ‐pyrrolo[2,1‐ b ]‐1,3‐oxazin‐7‐yl)malonates 5b , 5c , 5d , 5e , 5f (43–71%), or methyl 6‐oxo‐3,4‐dihydro‐2 H ,6 H ‐pyrido[2,1‐ b ]‐1,3‐oxazine‐7‐carboxylates 7a , 7b , 7c , 7d , 7e , 7f (32–59%), respectively. In these reactions, 1a , 1b , 1c , 1d , 1e , 1f (cyclic imidates, iminoethers) functioned as their N,C ‐tautomers (enaminoethers) 2 to α,β‐unsaturated esters 2 , 4, and 6 to give annulation products 3 , 5 , and 7 following to the elimination of methanol, respectively. J. Heterocyclic Chem., (2011).