Titanium Aryloxide Catalyzed Cross-Coupling and Oligomerization Reactions Involving 1,3-Cyclohexadiene, 1,3-Cyclooctadiene, and α-Olefins

The dimerization/oligomerization and cross coupling of 1,3-cyclohexadiene (1,3-CHD) with α-olefins can be achieved using a variety of titanium aryloxide catalysts. The titanabicyclic compound [Ti(OC6H3Ph4-2,3,5,6)2{CH2(C6H10)CH2}] initiates the rapid, non-Diels−Alder catalytic dimerization of 1,3-CHD to produce exclusively threo-5-(3-cyclohexenyl)-1,3-cyclohexadiene. Following dimerization of the majority of 1,3-cyclohexadiene into 8, the titanium catalyst then isomerizes (1,5-shift) 8 into 1-(3-cyclohexenyl)-1,3-cyclohexadiene 9 and eventually into a 70/30 mixture (GC analysis) of 9 and 2-(3-cyclohexenyl)-1,3-cyclohexadiene 10. Further cross coupling of dimers 8−10 with themselves and 1,3-CHD leads to trimers (C18 species) and tetramers (C24). This reaction can also be catalyzed by the dichlorides [Ti(OAr)2Cl2] (OAr = 2,6-diphenyl-, 2,3,5,6-tetraphenyl-, 2,6-diphenyl-3,5-dimethyl-, and 2,6-di-isopropyl-phenoxide) and [Cp(OAr)TiCl2] (OAr = 2,6-diphenyl-3,5-dimethyl-phenoxide) activated with 2 equiv of n-b...