Migratory insertion reactions of organometallics. 3. Carbon-carbon bond forming reactions of organotransition metals with .alpha.- or .gamma.-haloorganolithium reagents

Practical Enantioselective Arylation and Heteroarylation of Aldehydes with In Situ Prepared Organotitanium Reagents Catalyzed by 3‐Aryl‐H8‐BINOL‐Derived Titanium Complexes

“…A reasonable mechanism for the formation of 12 is given in Scheme . The first proposed step is the insertion of a 1,1‐dihalo‐1‐lithio species into 10 to form the ring‐expanded six‐membered zirconacycle 16 via 1,2‐metallate rearrangement of 15 9. 14 After addition of lithiated phenylacetylide to afford the ‘ate’ complex 17 ring closure occurs by 1,2‐bond migration to give intermediate 18 .…”

“…Elaboration of carbon–zirconium bonds by insertion of 1‐halo‐1‐lithio species (‘carbenoids’)8 was first reported for acyclic systems in 19899 and later applied to the ring expansion of zirconacyclopentanes and zirconacyclopentenes 1 to afford zirconacyclohexanes and zirconacyclohexenes 3 (Scheme ) 10. Since then a wide variety of carbenoids have been used,11 the regiochemistry of insertion into unsymmetric zirconacycles studied,12 and the chemistry applied to natural product synthesis 13.…”

Tandem Insertion of Halocarbenoids and Lithium Acetylides into Zirconacycles: A Novel Rearrangement to Zirconium Alkenylidenates by β‐Addition to an Alkynyl Zirconocene

“…The first proposed step is the insertion of a 1,1-dihalo-1-lithio species into 10 to form the ring-expanded six-membered zirconacycle 16 via 1,2-metallate rearrangement of 15. [9,14] After addition of lithiated phenylacetylide to afford the ate complex 17 ring closure occurs by 1,2-bond migration to give intermediate 18. From previous work [15] we know that the 1,2-rearrangement of the neutral intermediate 16 is slow at À78 8C, hence the requirement for the formation of 17 before rearrangement (Scheme 4).…”

“…[7] Elaboration of carbon-zirconium bonds by insertion of 1-halo-1-lithio species (carbenoids) [8] was first reported for acyclic systems in 1989 [9] and later applied to the ring expansion of zirconacyclopentanes and zirconacyclopentenes 1 to afford zirconacyclohexanes and zirconacyclohexenes 3 (Scheme 1). [10] Since then a wide variety of carbenoids have been used, [11] the regiochemistry of insertion into unsymmetric zirconacycles studied, [12] and the chemistry applied to natural product synthesis.…”

Cyclization reactions of ω‐tosyloxy‐1‐alkynyl‐ and ω‐tosyloxy‐1‐alkenylborates and their ω‐halo analogues

“…A THF solution of chloro (cyclohexyl)zirconocene, which was prepared by hydrozirconation of cyclohexene, was then added to the mixture at -1 20°C. After a few minutes, the reaction temperature was raised to 25°C over a few hours and cooled to -78°C [8]. After addition of 1, (1.5 equiv), the mixture was warmed to 25"C, and the desired iodide 19 was obtained in 48% yield based on dibromomethylenecyclopentane.…”