ChemInform Abstract: Reactions of Alkyl Magnesium Halides with Carboxylic Acid Esters in the Presence of Tetraisopropoxy Titanate.

Abstract

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Carbocyclic Amino Ketones by Bredt's Rule‐Arrested Kulinkovich–de Meijere Reaction

“…The extraordinary coupling of an alkene and an ester to give cyclopropanols, mediated by low‐valent titanium, has been extensively studied since its discovery in 1989 by Kulinkovich, and was extended to tertiary amides in 1996 by de Meijere to yield cyclopropylamines (Scheme ) . These powerful transformations have been pivotal in syntheses of natural products and pharmaceutical agents .…”

Stereocontrolled alkylation of unsaturated compounds with alkoxytitanacyclopropane reagents

“…Preferable formation of cis ‐1,2‐disubstituted cyclopropanols cis‐ 2 is a distinctive stereochemical feature of the cyclopropanation of carboxylic esters with substituted alkoxytitanacyclopropane reagents (Scheme ) 3b,9,17,18. The stabilizing α‐agostic interaction of the titanium atom with geminal hydrogen in the transition state of the cyclopropane ring‐closure step was proposed as a possible driving force of the cis ‐diastereoselectivity on the basis of DFT calculations 10.…”

“…In the late 1980s, we described the reaction of carboxylic esters with ethylmagnesium bromide and its higher homologs in the presence of titanium(IV) isopropoxide, which resulted in the formation of tertiary cyclopropanols 2 in good to excellent yields (Scheme ) 3. It was supposed that the key 1,2‐dicarbanionic equivalents in this transformation were diisopropoxytitanacyclopropane intermediates 3 , formed as a result of the disproportionation of thermally unstable dialkyltitanium precursors 4 .…”

General Synthesis of Cyclopropanols via Organometallic Addition to 1-Sulfonylcyclopropanols as Cyclopropanone Precursors

“…For example, the pluripotential of cyclopropanols was recently demonstrated via late-stage functionalization, affording different derivatives of chlamydocin, a histone deacetylase inhibitor . Despite the obvious relevance of cyclopropanols in the construction of biologically relevant molecules, the development of novel and general methods for the formation of enantioenriched tertiary derivatives, , leading to β-nucleophilic ketone equivalents, has remained scarce. , The most conventional approaches to tertiary cyclopropanols include the cyclopropanation of enols using carbenoid species (Scheme a) ,, or the Kulinkovich cyclopropanation of esters (Scheme b), − both of which are rarely amenable to the formation of enantioenriched products and possess considerable limitations in terms of practicality and sustainability . A distinct approach, which consists of introducing the C(1)-substituent last via nucleophilic addition to a cyclopropanone surrogate, is not general mainly due to the absence of suitable precursors readily accessible in enantioenriched form (Scheme c).…”