
TY  - JOUR
A1  - Buttery, JH 
A1  - Moursounidis, J 
A1  - Wege, D 
T1  - A,B-Diheteropentalenes by a Tandem Intramolecular Diels-Alder/Reverse Diels-Alder Reaction Sequence. Application to the Synthesis of Thieno[3,4-b]furan
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1995
VL  - 48
IS  - 3
SP  - 593
EP  - 607
KW  - 
UR  - https://doi.org/10.1071/CH9950593 
N2  - Alkylation  of 2-furylmethanethiol (28) with propargyl chloride gave the thioether (22) which on methoxycarbonylation afforded the acetylenic ester (30). On heating, this material underwent an intramolecular Diels -Alder reaction to give the tricyclic compound (32). In the presence of 3,6- di (pyridin-2&#8242;-yl)-s- tetrazine , (32) afforded methyl 4,6-dihydrothieno[3,4-b]furan-3-carboxylate (38) by a sequence involving a further Diels -Alder reaction followed by two reverse Diels-Alder reactions. The ester (38) could be dehydrogenated to give methyl thieno [3,4-b]furan-3-carboxylate (40) while hydrolysis of (38), followed by decarboxylation and dehydrogenation delivered the parent thieno [3,4-b]furan (5). 3-Methyl-4,6-dihydrothieno[3,4-b]furan (46) and 3-methylthieno[3,4-b]furan (47) were prepared; a comparison of the 4JMe-C=C-H coupling constants in the 1H n.m.r . spectra of (46) and (47) suggests that an increase in the C2-C3 furyl bond order accompanies the (46) &#8594; (47) conversion. Methyl 4,6-dihydrofuro[3,4-b]furan-3-carboxylate (39), 4,6-dihydrofuro[3,4-b]furan (27) and methyl 4,6-dihydro-6-phenylfuro[3,4-b]furan-3-carboxylate (53) were prepared by an analogous tandem reaction sequence. These compounds could not be dehydrogenated to the fully conjugated furo [3,4-b]furan ring system. 
ER  -

