Spirocyclopropanated Bicyclopropylidenes: Straightforward Preparation, Physical Properties, and Chemical Transformations

摘要

Perspirocyclopropanated bicyclopropylidene (6) was prepared in three steps from 7-cyclopropylidenedi-spiro[2.02.1]heptane (4)(24% overall) or, more efficiently, through dehaloge-native coupling of 7,7-dibromo[3]train-gulane (15) (82%). This type of reductive dimerization turned out to be successful for the synthesis of (E)-and (Z)bis(spiropentylidene) 14 (67%) and even of the "third-generation" spirocyclopropanated bicyclopropylidene 17 (17% overall from 15). Whereas the parent bicyclopropylidene 1 dimerized at 180deg C to yield [4]rotane, dimerization of 6 at 130deg C under 10kbar pressure occurred only with opening of one threemembered ring to yield the polyspirocyclopropanated (cyclopropylidene)cyclo-pentane derivative 19 (34% yield), and at the elevated temperature the polyspirocyclopropanated 2-cyclopropylidene[3.2.2]propellane derivative 20 (25% yield). Perspirocyclopropanated bicyclopropylidene 6 and the "third generation" bicyclopropylidene 17 gave addition of bromine, hydrogen bromide, and various dihalocarbenes without rearrangement. The functionally substituted branched [7]triangulane 28 and branched dichloro-C_(2v)-[15]triangulane 32 were used to prepare the perspirocyclopropanated [3]rotane (D_(3h)-[10]train-gulane) 49 (six steps from 6, 1.4% overall yield) and the C_(2v)-[15]triangu-lane 51 (two steps from 17,41% overall). Upon catalytic hydrogenation, the perspirocyclopropantted bicyclopropylidene 6 yielded 7,7'-bis(dispiro[2.0.2.1]heptyl) (52) and, under more forcing conditions, 1,1'-bis(2,2,3,3-tetramethylcyclopropyl) (53). The bromofluorocarbene adduct 33 of 17 reacted with butyllithium to give the unexpected polyspirocyclopropanated 1,4-di-n-butyl-2-cyclopropylidenebicyclo[2.2.0]hexane derivative 37 as the main product(55% yield) along with the expected "third-generation" perspirocyclopropanated dicyclopropylidenemethane 38 (21% yield). Mechanistic aspects of this and the other unusual reactions are discussed. The structures of all new unusual hydrocarbons were proven by X-ray crystal structure analyses, and the most interesting structural and crystal packing features are presented.