CIS-FUSED DIHYDROFURANO-1,2,4-TRIOXANES

The endoperoxide obtained from 2,5-diphenylfuran at -30 degrees C on c atalysis with trimethylsilyl trifluoromethanesulfonate condenses with pivalaldehyde, acetone and cyclohexanone to give the corresponding cis -fused dihydrofurano-1,2,4-trioxanes (20, 21, 22 and 23) respectively in yields not greater than 27%. The reaction of pivalaldehyde with the endoperoxide derived from 1,4-diphenyl 1,3-cyclopentadiene gives the cis and trans-3-tert-butyl substituted cis-fused cyclopenteno-1,2,4-tr ioxanes (26 and 27) in 75% yield. The structures of 22, 23, 26 and 27 are determined by X-ray.