Titanium-mediated synthesis of conjugated dienes

doi:10.1016/S0040-4039(00)74304-8

Tetrahedron Letters

Volume 32, Issue 14, 1 April 1991, Pages 1687-1690

https://doi.org/10.1016/S0040-4039(00)74304-8 Get rights and content

Abstract

Titanacyclobutenes, readily prepared from Cp₂TiCH₂·Al(CH₃)₂Cl and alkynes, react with ketones and aldehydes to afford metallacyclic products resulting from insertion into either the titanium-alkyl or the titanium-vinyl bond of the titanacyclobutene. The latter insertion products are thermally unstable, undergoing facile retro [4+2] cycloaddition to afford substituted 1,3-dienes in good yield.

Aldehydes and ketones insert preferentially into the titanium-vinyl bond of titanacyclobutenes. Thermal decomposition of the insertion products via facile retro [4+2] cycloaddition generates conjugated dienes.

References (11)

I. Iwai et al.
Org. Syn.
(1970)
K.M. Doxsee et al.
Organometallics
(1990)
F.N. Tebbe et al.
J. Am. Chem. Soc.
(1978)
J.D. Meinhart et al.
J. Am. Chem. Soc.
(1986)
J.D. Meinhart
(1987)
R.J. McKinney et al.
J. Am. Chem. Soc.
(1981)
R.S. Tanke et al.
Inorg. Chem.
(1989)

There are more references available in the full text version of this article.

Cited by (40)

Regioselectivity of metallacycle formation via intramolecular CH activation
2000, Polyhedron
Carbometalation of alkynes by dimethyltitanocene affords vinyl complexes which serve as intermediates for the formation of titanacyclic products through subsequent hydrogen abstraction/methane elimination. Although multiple sites for hydrogen abstraction are present in the intermediate vinyl complexes, the hydrogen abstraction step is in most cases highly regioselective, leading to the formation of either titanacyclobutenes (via γ-H abstraction) or titanacyclopropanes (via β-H abstraction). Rotational isomerization, restricted in the case of larger vinyl group substituents, provides a simple and consistent explanation for the observed regioselectivities, and this effect is sufficiently pronounced to lead to preferential γ-aliphatic CH activation even in the presence of γ-aromatic hydrogens. The titanacyclopropanes may be alternatively formulated as allene complexes of titanocene. An independently prepared trimethylphosphine-ligated analog of 3-methyl-1,2-butadiene, representing the first titanocene allene complex to be reported, undergoes reductive coupling reactions with excess 3-methyl-1,2-butadiene and with alkynes.
Terminal chalcogenido complexes of zirconium: Syntheses and reactivity of Cp<inf>2</inf>*Zr(E)(NC<inf>5</inf>H<inf>5</inf>) (E = O, S, Se, Te)
1997, Journal of Organometallic Chemistry
The terminal zirconium chalcogenido complexes Cp₂^*Zr(E)(NC₅H₅)(Cp^* = η⁵-C₅Me₅; E = O, S, Se, Te) are conveniently synthesized by the reactions of Cp₂^*Zr(CO)₂ with either N₂O or the elemental chalcogen (S, Se, Te) in the presence of pyridine. The [Zr=E] functionalities in these complexes are highly reactive and undergo a variety of 1,2-addition and cycloaddition reactions, resulting in a diverse array of products. For example, reactions of the zirconium oxo complex Cp₂^*Zr(O)(NC₅H₅) yield Cp₂^*Zr(OH)₂, Cp₂^*Zr(η²-O₂CMe)(η¹-OCOMe), Cp₂^*Zr(OPh)₂, Cp₂^*Zr(OH)(NH₂), Cp₂^*Zr(OH)(NHPh), Cp₂^*Zr(OH)[η²-N(Ph)NH₂], Cp₂^*Zr(H)(OSiH₂Ph), [Cp₂^*Zr(H)](μ-O)[Cp₂^*Zr(OH)], Cp₂^*Zr(OH)[η¹-OC(R)=CH₂] (R = Me, Ph, Bu^t), Cp₂^*Zr(OH)I, Cp₂^*Zr(OMe)I, Cp₂^*Zr(OSiMe₃)Cl, Cp₂^*Zr[η²-OCH(R)OCH(R)O] (R = H, Prⁱ, Bu^t), and Cp₂^*Zr[η²-OC(Ph)NC(Ph)N].
Tris(trimethylsilyl) titanacyclobutene: A new mild reagent for the conversion of carbonyls to alkenyl silanes
1995, Tetrahedron Letters
Thermolysis of Cp₂Ti(CH₂SiMe₃)₂ in the presence of Me₃SiCCSiMe₃ forms tris(trimethylsilyl) titanacyclobutene. Unlike other titanacyclobutenes which undergo insertion with carbonyl compounds, this reagent serves as a precursor to Cp₂TiCHSiMe₃, converting carbonyl compounds to the corresponding alkenyl silanes. This olefination takes place under mild conditions even at room temperature and works with aldehydes, ketones, esters, thioesters and lactones.
α-Diimine synthesis via titanium-mediated multicomponent diimination of alkynes with C-nitrosos
2022, Chemical Science
Fluoroalkenylation of boronic acids: Via an oxidative Heck reaction
2019, Organic and Biomolecular Chemistry
Synthesis, Cycloaddition, and Cycloreversion Reactions of Mononuclear Titanocene-oxo Complexes
2016, Organometallics

View all citing articles on Scopus

View full text

Titanium-mediated synthesis of conjugated dienes

Abstract

Org. Syn.

Organometallics

J. Am. Chem. Soc.

J. Am. Chem. Soc.

J. Am. Chem. Soc.

Inorg. Chem.