Triene electrocyclizations: Some structure reactivity relations☆

摘要: Abstract Two stereoselective routes for the synthesis of trienes having a central cis double bond have been devised. These were employed (Z)-1-(cyclohexen-1-yl)-1,3-butadiene ( 1 ), (Z,E)-1-(cyclohexen-1-yl)-1,3-pentadiene 2 (Z,Z)-1-(cyclohexen-1-yl)-1,3-pentadiene 3 1,2-divinyleyclohexene 4 (E,Z)-1-phenyl-1,3,5-hexatriene 5 (Z,Z)-1-phenyl-1,3,5-hexatriene 6 ) and (E,Z)-1-( p -chlorophenyl)-1,3,5-hexatriene 7 ). Rates thermal electrocyclization activation parameters measured these in inert solvents. The results are tabulated below. Compound k x 10 (sec −1 Temp (°C) Δ H ‡ S 12·8 132 29 −6 12·5 2·6 173 34 −5 3·86 125 25 −15 16·0 145 28 −8 3·0 195 15·0 −18(?) their implications transition state geometry considered.