ISSN:
0009-2940
Keywords:
Pentalenes, dihetero-
;
Cyclizations, 1,7-dipolar
;
Carbonyl ylides
;
Cycloallenes
;
Diels-Alder reactions
;
o1-Quinodimethanes, hetero analogues
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
A Novel Route to Isoannulated Heteroaromatic Compounds, 1. - Synthesis and Reactions of Furofurans, Thienofurans, Furobenzofurans, and BenzothienofuransA general method for the synthesis of furo-and thienofurans 4-7 has been developed. The reaction principle is based on the thermal transformation of suitably structured epoxyhexenynes (15-19) following the general reaction sequence 1→2→3 (annulation type A). Derivatives of the so far unknown diheteropentalenes furo[3,4-b]furan (4b, c, d, g, h), furo-[3,4-b]benzofuran (6b, d, e, 45) as well as benzo[4,5]thieno-[2,3-c]furan (7b, d) are obtained by short-time thermolysis. Likewise two representatives of the previously reported thieno[2,3-c]furan system are prepared (5b, c). By flash vacuum thermolysis the benzo-annulated epoxyhexenyne 19b rearranges in poor yield to the isobenzofuran 52 (identified as dimethyl acetylenedicarboxylate adduct 47) and 2-cyano-α1-naphthol (46). The structure of the furo[3,4-b]furan 4b has been established by X-ray structural analysis. A mechanistic explanation of the transformation of the epoxyhexenynes to diheteropentalenes is proposed. Indications for the occurrence of carbenes as product-determining species are obtained with the phenylcyano-substituted oxiranes 15c, h and 17e which - in additon to the furofurans 4c, h and 6e - lead to the furylindenes 31c, h/32c, h and 41, resp. The Diels-Alder reactivity of the furo-and thienofurans 4g, 5b, c, and 6b has been examined.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19931260419
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