Studies on the Synthesis of Furocoumarins. Part-XXX. A Reinvestigation of Claisen Rearrangement of 7-Cinnamyloxy-4-methylcoumarin

Department of Chemistry, Faculty of Science, M. S. University of Baroda, Baroda-390 002

Manuscript received 24 October 1991, accepted 23 March 1992

7-annamylozy. 8-methylcoumarin on Claisen migration gave three products. trans-3, 7-dimethyl 2-phenyl-2 3- dihydrofurel-[2,3-b]Abenzopyran 5[H]-one (la), 7 hydroxy 4-methyl 8-(1'-phenylprop-1'-ene)coumarin (1e) and 7 by drozy 4 methyl 6 (1' phenyiprop 2 -ene)coumariu (if) le and If on cyclisation with H₂SO₄ gave 2b and 3a respectively 2a 2b and 3a on dehydrogenation with either DDQ in dry benzene or Pd C (104,) in diphenyl ether gave 4a 4b and 5b respectively. In a similar way 2,5,9-trimethyl-3 phenylfuro[3,2-g]benzopyran 7[H] one (5c) was also synthesised. Structures of the compounds were confirmed by ¹H nmr spectra and cis and trans-stereo-chemistry of dibydrofurocoumarins was established by aOe difference spectra.