Dn. Nicolaides et al., REACTIONS OF 4,6-BIS(ACETYL)RESORCINOL WITH ALKOXYCARBONYLALKYLIDENE(TRIPHENYL)PHOSPHORANES - PREPARATION OF COUMARIN DERIVATIVES, Journal of heterocyclic chemistry, 31(1), 1994, pp. 173-176
Reaction of compound 1 with ylide 2a affords compounds 3a, 3b and coum
arins 4a, 5a, 5b, 6a in 77% total yield. Reaction of 1 with ylide 2b a
ffords coumarin 4b. The acetylderivatives obtained, react further with
ylides 2a-c to give pyrano[3,2-g]chromene-2,8-diones 6b-d.