The Reaction of Dihalocarbenes with Quadricyclane

Article abstract of DOI:10.1002/hlca.19850680607

The reaction of difluoro-, dichloro- and dibromocarbene with quadricyclane (2) were examined.In all cases, conversions were low (4-15percent), but three distinct reaction courses were observed: cleavage, 1,2-addition, and 1,4-addition.Difluorocarbene gave mainly 6-endo-(2,2-difluorovinyl)-cis-bicyclo<3.1.0>hex-2-ene (8; 52-89percent relative yield), together with minor amounts of exo-3,3-difluorotricyclo<3.2.1.0^2,4>oct-6-ene (7; 13-17percent), and 4,4-difluorotetracyclo<3.3.0.0^2,8.0^3,6>octane (5; 2-4percent).Dichlorocarbene gave analogous products, but in relative yields of 35(17), 51(11), and 12percent(16).The product 11 of 1,2-exo addition underwent furtherrearrangement to its allylic derivative 12.A small amount of 1,2-endo addition also occured (2percent of 14/15).Dibromocarbene gave predominantly products derived from rearrangement of the 1,2-exo (61percent of 20/21) and, 1,2-endo adducts (10percent of 23/24).In addition, a significant amount of 4,4-dibromotetracyclo<3.3.0.0^2,8.0^3,6>octane (25; 21percent) was formed.The cleavage product, 6-endo-(2,2-dibromovinyl)-cis-bicyclo<3.1.0>hex-2-ene (26) was also observed (7percent).The yields and product compositions were compared to those obtained from norbornadiene (1) and found to be entirely different (Table 1) for example no cleavage occured with difluorocarbene.