Mechanistic study of ester olefinations using dimethyltitanocene

David L. Hughes; Joseph F. Payack; Dongwei Cai; Thomas R. Verhoeven; Paul J. Reider

doi:10.1021/om9507843

Mechanistic study of ester olefinations using dimethyltitanocene

David L. Hughes, Joseph F. Payack, Dongwei Cai, Thomas R. Verhoeven, Paul J. Reider

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Abstract

Olefination of esters using dimethyltitanocene is proposed to proceed via the titanium carbene, Cp₂Ti=CH₂, on the basis of the following evidence: (1) No H/D exchange or ¹³C scrambling occurs in the reactions of ethyl acetate or dodecyl acetate using either labeled ester or labeled dimethyltitanocene, (2) kinetics are zero order in ester and first order in Cp₂TiMe₂, (3) the reactions of ethyl acetate and dodecyl acetate with Cp₂Ti(CD₃)₂ produce substantial kinetic isotope effects of 9-10, (4) esters of differing electronic and steric environments have similar reactivity, and (5) there is regiochemical preference for the least stable exo-methylene product. These findings are inconsistent with the methyl addition mechanism proposed in the literature.

Original language	English (US)
Pages (from-to)	663-667
Number of pages	5
Journal	Organometallics
Volume	15
Issue number	2
DOIs	https://doi.org/10.1021/om9507843
State	Published - Jan 23 1996
Externally published	Yes

All Science Journal Classification (ASJC) codes

Physical and Theoretical Chemistry
Organic Chemistry
Inorganic Chemistry

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title = "Mechanistic study of ester olefinations using dimethyltitanocene",

abstract = "Olefination of esters using dimethyltitanocene is proposed to proceed via the titanium carbene, Cp2Ti=CH2, on the basis of the following evidence: (1) No H/D exchange or 13C scrambling occurs in the reactions of ethyl acetate or dodecyl acetate using either labeled ester or labeled dimethyltitanocene, (2) kinetics are zero order in ester and first order in Cp2TiMe2, (3) the reactions of ethyl acetate and dodecyl acetate with Cp2Ti(CD3)2 produce substantial kinetic isotope effects of 9-10, (4) esters of differing electronic and steric environments have similar reactivity, and (5) there is regiochemical preference for the least stable exo-methylene product. These findings are inconsistent with the methyl addition mechanism proposed in the literature.",

author = "Hughes, {David L.} and Payack, {Joseph F.} and Dongwei Cai and Verhoeven, {Thomas R.} and Reider, {Paul J.}",

year = "1996",

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doi = "10.1021/om9507843",

language = "English (US)",

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T1 - Mechanistic study of ester olefinations using dimethyltitanocene

AU - Hughes, David L.

AU - Payack, Joseph F.

AU - Cai, Dongwei

AU - Verhoeven, Thomas R.

AU - Reider, Paul J.

PY - 1996/1/23

Y1 - 1996/1/23

N2 - Olefination of esters using dimethyltitanocene is proposed to proceed via the titanium carbene, Cp2Ti=CH2, on the basis of the following evidence: (1) No H/D exchange or 13C scrambling occurs in the reactions of ethyl acetate or dodecyl acetate using either labeled ester or labeled dimethyltitanocene, (2) kinetics are zero order in ester and first order in Cp2TiMe2, (3) the reactions of ethyl acetate and dodecyl acetate with Cp2Ti(CD3)2 produce substantial kinetic isotope effects of 9-10, (4) esters of differing electronic and steric environments have similar reactivity, and (5) there is regiochemical preference for the least stable exo-methylene product. These findings are inconsistent with the methyl addition mechanism proposed in the literature.

AB - Olefination of esters using dimethyltitanocene is proposed to proceed via the titanium carbene, Cp2Ti=CH2, on the basis of the following evidence: (1) No H/D exchange or 13C scrambling occurs in the reactions of ethyl acetate or dodecyl acetate using either labeled ester or labeled dimethyltitanocene, (2) kinetics are zero order in ester and first order in Cp2TiMe2, (3) the reactions of ethyl acetate and dodecyl acetate with Cp2Ti(CD3)2 produce substantial kinetic isotope effects of 9-10, (4) esters of differing electronic and steric environments have similar reactivity, and (5) there is regiochemical preference for the least stable exo-methylene product. These findings are inconsistent with the methyl addition mechanism proposed in the literature.

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Mechanistic study of ester olefinations using dimethyltitanocene

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