X-Ray structure of a novel product formed from 2,5-dimethylhex-3-yne-2,5-diol by catalytic action of dibromobis(triphenylphosphine)nickel

Abstract

When heated under reflux in toluene in the presence of [(Buⁿ₃P)₂NiBr₂], 2,5-dimethylhex-3-yne-2,5-diol is not converted into the expected simple polymerization product. X-Ray structural analysis shows the novel product to be 1′-(1,3-dihydro-7-isopropenyl-6-isopropyl-1,1,4,4-tetramethylfuro[3,4-c]pyran-3-ylidenemethyl)-1,3-dihydro-7-isopropenyl-6-isopropyl-1,1,4,4,5′,5′-hexamethylfuro[3,4-c]pyran-3-spiro-3′-cyclohexene, in agreement with other physical data. The same product was obtained with [(Ph₃P)₂NiBr₂] as catalyst. Crystals are monoclinic, a= 9.32(1), b= 37.26(3), c= 13.18(1)Å, β= 118.7(1)°, Z= 4, space group P2₁/c. The structure was solved from diffractometer data by direct methods and refined to R 0.054 for 3 583 observed reflections.