Titanium(IV) Isopropoxide-Catalyzed Formation of 1-Substituted Cyclopropanols in the Reaction of Ethylmagnesium Bromide with Methyl Alkanecarboxylates

Abstract

Titanium(IV) Isopropoxide-Catalyzed Formation of 1-Substituted Cyclopropanols in the Reaction of Ethylmagnesium Bromide with Methyl Alkanecarboxylates

Synthetic Applications of Intermolecular Cyclopropanation of Carboxylic Esters with Dialkoxytitanacyclopropane Reagents

“…The observation that an additional equivalent of the Grignard reagent was necessary in the noncatalytic reaction to achieve good yields of cyclopropanols, together with a similar finding in the reaction of titanacyclopropane 1 with allylic alcohol derivatives, [19] led to the proposal [20] that addition of a Grignard reagent to complex 10 initiates the formation of the carbonϪcarbon bond to give the titanacyclopentane complex 14 (Scheme 6). Fragmentation of the latter affords the β-oxotitanium derivative 15, which ring-closes to titanium cyclopropanolate 16, which, as in the first proposed mechanism, [5,6] further transforms into the diethyltitanium derivative 8 and magnesium cyclopropanolate 13. If the alkoxide group at the titanium atom is considered to be a 6e ligand, it can be concluded that the complex 14 and the titanacyclopropaneϪester complex 10 are 18e organometallic species, whereas oxatitanacyclopentane 11 is a 16e organometallic species.…”

“…[4,5] We found that the interaction of ethylmagnesium bromide with isopropoxytitanium butyrate (6), which was being studied as a model ZeiglerϪNatta process, results in the formation of 1-propylcyclopropanol (7) (Scheme 3). [5] Although the latter was ob- tained as a minor product in low yield, our experience in the chemistry of cyclopropanes [17,18] allowed us to foresee the considerable potential of this unusual reaction and impelled us to investigate the reaction systematically.…”

“…For example, cyclopropanol 7 was prepared from methyl butyrate (9) in 90% isolated yield (Scheme 5). [4,5] When the order of reagent mixing was reversed, that is, the organomagnesium compound was added to the mixture of the ester and titanium() isopropoxide, the reaction occurred catalytically with 0.05Ϫ0.1 equiv. of titanium() isopropoxide.…”

Highly Enantio- and Diastereoselective Synthesis of 2-Substituted 1-Bicyclo[3.1.0]hexanols

“…The reaction of unsaturated esters, [4] amides, [5] imides, [6] and related compounds [7] with an alkene ± titanium complex [8] is a very convenient method to prepare bicyclic cyclopropanols [4] and cyclopropylamines [5] in one step [Eqs. (1) and (2); X R'O, Cl, Br].…”

Two New Isopolyoxotungstates(VI) with the Empirical Composition Cs2W2O7⋅2 H2O and Na2W2O7⋅H2O: An Icosatetratungstate and a Polymeric Compound

“…The molar ratio of H introduced to WO 2À 4 is defined as the degree of acidification of the metalate solution, the molar ratio of H that reacted per WO 2À 4 is the degree of protonation. [8] …”