Generation and intermolecular trapping of a cage-annulated cycloalkylidenecarbene

Base-promoted reaction of 11-methylenepentacyclo [5.4.0.0(2.6).0(3,10).0(5, 9)]undecan-8-one (5) with diethyl diazomethylphosphonate when performed in the presence of excess cyclohexene, resulted in the formation of the corres ponding cycloalkylidenecarbene, 6, which subsequently was trapped in situ t o afford 8-methylene-11-(7'-bicyclo[4.1.0]heptylidene)pentacyclo- [5.4.0.0( 2,6).0(3,10).0(5,9)]undecane (7, obtained in 44% yield as a mixture of exo, endo isomers). Subsequent reaction of 7 with dichlorocarbene (generated un der phase transfer catalytic conditions) produced the corresponding mono- a nd di-:CCl2 adducts [i.e., 8 (64% yield) and 9 (5% yield), respectively]. T he structure of 9 was established unequivocally via application of single c rystal X-ray analysis: Triclinic, P (1) over bar, a = 6.276(2), b = 8,700(2 ), c = 18.550(3) A, alpha = 76.52(3), beta = 87.59(3), gamma = 70.88(4)degr ees; Z = 2; D-calc 1.486 g cm(-3).