Studies in the Synthesis of Furocoumarins : Part (XXIV) Synthesis of Difurocoumarin Derivatives

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

Manuscript received 2 September 1977, revised 4 July 1978, accepted 30 August 1978

4-Hydroxy-7-allyloxycoumarin(Ia), on allylation and Claisen rearrangement gave 7-allyioxy-2-
methyl-2,3-dihydro-4-oxo-4H-furo(3,2-c)benzopyran(IIa) and 7-hydroxy-6- allyl-2-methyl-2,3-dihydro
-4-oxo-4H-furo(3,2-c)benzopyran(IIb). (IIa), on further Claisen rearrangement gave (IIb) which on
cyclisation followed by dehydrogenation afforded 2,7-dimethy1-4-oxo-4H-difuro(3,2-c : 2',3'-h)
benzopyran(IV). 2,6,8-Trhuethy1- 4.oxo-4H-difuro(3,2-c : 3',2'-g)benzopyran(V) and 2,9-dimethyl
-4-oxo-4H-difuro­(3,2-c : 3',2'-benzopyran(VII) were similarly synthesised from 4-hydroxy-7-allyloxy­
8-methylcoumarin(lc) and 4-hydroxy-6-allyloxycoumarin(Ie) respectively.