Thieno furan synthesis

Thieno[3,4-d][l,3]dithiol-2-one, 1-nitro-synthesis, 6, 1013 Thieno[3,4-c]furan, 4,6-dichloro-synthesis, 6, 1013 Thieno[3,4-c]furan, tetraphenyl-formation, 4, 1060 synthesis, 4, 1060 UV spectra, 4, 1044 Thieno[3,2-6]furans structure, 4, 1039 synthesis, 6, 1020 Thieno[3,4-c]furans... 

The method has been extended to o-hydroxyaryl ketones for the synthesis of naphtho[l,2-6]furanes,656 thieno[3,2-e]benzofurans,657 furo-flavones,658 furoxanthones,659 furoquinolines,611,660 phenanthrofur-ans,660 and other complex benzofurans.661... 

Over the last few decades there has been much interest in the thiophene-based systems and considerable effort has been expended in many laboratories on various aspects of their chemistry, including synthesis, structural studies and theoretical calculations and predictions. X-Ray analysis of the crystal structures of thieno[3,2-6]thiophene (3) (49AX356), selenolo[3,2-6]selenophene (4) (69AX(B)1374) and thieno[3,2-6]furan derivative (5) (79CC366) have been reported. 

A total synthesis of the mold metabolite ethisolide <86TL445> (404) has been described. Two reduced thieno[3,4-/>]furan systems have been prepared to test their value as food flavorings (405) <70GEP(0)1964803> and as antiinflammatory agents (406) <73GEP(O)2238204>. 

Acid catalysed cyclisation of the substituted furans 20 led to formation of the spiro-systems 21 and 22, the latter being formed preferably <97TL7641>. Other syntheses involving the intermediacy of an oxonium ion include the preparation of thieno[2]azepines <97JHC1494>, l,2,3,4-tetrahydro-5//-l-benzazepine-6,9-quinones <97H(45)1703> and a new synthesis of ( )-cis- and ( )-/ra 8-clavicipitic acid <97T51 >. 

---