| Abstract
| - [(DMSC)Ti{1,2,4-(Me3Si)3C6H3}] (1) mediates an unusual coupling of terminal alkynes with ketones to produce 2,7-dioxa-1-titana-4-cycloheptenes. The regioselectivity of the reaction is controlled by the DMSC ligand, which enforces exo-orientation of the alkyne non-H substituent in the putative intermediate (DMSC)Ti(η2-alkyne) species.
- Reaction of [(DMSC)Ti{1,2,4-(Me3Si)3C6H3}] (1) with 1 equiv of bipyridine (bpy) or 4,4‘-dimethyl-2,2‘-dipyridyl (dmbpy) and a slight excess of RC⋮CH quantitatively produced[(DMSC)Ti(η2-RC⋮CH)(L2)] (L2 = bpy or dmbpy) (5−16). (DMSC)TiPh2 (17) reacted with≥2 equiv of bpy or dmbpy to give (DMSC)Ti(bpy)2 (18) and (DMSC)Ti(dmbpy)2 (19),respectively. Both 1H and 13C NMR data, as well as X-ray crystallography in the case of[(DMSC)Ti(η2-HC⋮CBut)(bpy)] (7), support exo-orientation of the alkyne's non-H substituentin 5−16. Reaction of [(DMSC)Ti{1,2,4-(Me3Si)3C6H3}] (1) with a mixture of RC⋮CH andR2CO did not give the expected 5-oxa-1-titana-2-cyclopentene products but instead produced2,7-dioxa-1-titana-4-cycloheptenes (20−25). The latter result may be understood in termsof the unique directing influence of the DMSC ligand.
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