Synthesis, Table of Contents PAPER © Georg Thieme Verlag Stuttgart · New York Synthesis of Linear Heterocycles: Thermal Sigmatropic Rearrangement of 4-(4-Aryloxybut-2-ynyloxy)[1]benzopyran-2-thiones K. C. Majumdar*, G. H. JanaDepartment of Chemistry, University of Kalyani, Kalyani 741 235, West Bengal, Indiae-Mail: kcm@klyuniv.ernet.in; Recommend Article Abstract Buy Article All articles of this category Abstract A number of 4-(4-aryloxybut-2-ynyloxy)[1]benzopyran-2-ones 6a-h were converted to corresponding thiones 4a-h. The thiones 4a-h in refluxing 1,2-dichlorobenzene gave 4-aryloxymethylthiopyrano[2,3-b][1]benzopyran-5(2H)-ones 5a-d and products 7a-d in 20-26% and 50-55% yield, respectively, whereas thiones 4e-h furnished exclusively products 7e-h in 80-85% yield. Addition of radical initiator azobisisobutyronitrile or radical scavenger hydroquinone or acid or base does not seem to have any effect on the rearrangement. All the butynyl ethers studied so far underwent sigmatropic rearrangements at the 4-coumarin-4-yloxypropynyl function of compounds 4a-h to give products 5a-d and or 7a-h. Key words cyclizations - heterocycles - sigmatropic rearrangement - thionation - thiopyrano[2,3-b][1]benzopyran-5-ones Full Text References References 1 Audus LJ. Quastel JH. Nature 1947, 159: 320 2a Feuer G. Progress in Medicinal Chemistry Ellies GP. West GB. North-Holland Publishing Company; New York: 1974. 2b Lauger PV. Martin H. Muller P. Helv. Chim. Acta 1944, 27: 892 2c Kitagawal H. Iwaki R. Yanagi B. Sato T. J. Pharm. Soc. (Japan) 1956, 76: 186 2d Dean FM. Naturally Occuring Oxygen Ring Compounds Butterworths; London: 1963. 2e Soine TO. J. Pharm. Sci. 1964, 53: 231 2f Link KP. Fed. Proc. Fed. Am. Soc. Exp. Biol. 1945, 4: 176 2h Mentzer C. Vinet MA. Helv. Chim. Acta 1964, 29: 1291 3 Deena AA. J. Med. Chem. 1983, 26: 580 4a Gordon M. Grover SH. Strothers JB. Can. J. Chem. 1973, 51: 2092 4b Wenkert E. Buckwalter BL. J. Am. Chem. Soc. 1972, 94: 4367 5a Wawzoneck S. In Heterocyclic Compounds Vol. 2: Elderfield RC. Wiley; New York: 1952. p.176 5b Staunton J. In Comprehensive Organic Chemistry Vol. 4: Sames PG. Pergamon Press; Oxford: 1979. p.646 5c Hepworth JD. In Comprehensive Heterocyclic Chemistry Boulton AJ. McKillop A. Pergamon Press; Oxford: 1984. p. 799 6 Majumdar KC. Khan AT. DeR N. Synth. Commun. 1988, 18: 1589 7 Majumdar KC. Das DP. Khan AT. Synth. Commun. 1988, 18: 2027 8a Majumdar KC. Das DP. Jana GH. Khan AT. Indian J. Chem. 1994, 33B: 120 8b Majumdar KC. Das DP. Jana GH. Synth. Commun. 1993, 23: 2171 8c Majumdar KC. Jana GH. Heterocycles 1996, 43: 767 9a Majumdar KC. DeR N. Khan AT. Chattopadhyay SK. Dey K. Patra A. J. Chem. Soc., Chem. Commun. 1988, 777 9b Majumdar KC. DeR N. J. Chem. Soc., Perkin Trans. 1 1989, 1901 10 Majumdar KC. Choudhury PK. Synth. Commun. 1993, 23: 1087 11 Majumdar KC. Khan AT. Saha S. Synth. Commun. 1992, 22: 901 12 Ramakanth S. Narayanan K. Balasubramanian KK. Tetrahedron Lett. 1984, 25: 103 13 Majumdar KC. Khan AT. Saha S. Synlett 1991, 595
