Enals directed electrostatic

Enantioselective organocatalytic cyclopropanations have been performed using directed electrostatic activation conditions.164 Using a new class of iminium catalysts, cyclopropanation has been conducted with enals but not electron deficient alkenes, such as unsaturated nitrile, nitro, or alkylidene malonate systems. 

A novel method for enantioselective organocatalytic cyclopropanation has been developed, using a new class of iminium intermediates and based on the concept of directed electrostatic activation (DEA). This novel organocatalytic mechanism exploits dual activation of ylide (153) and enal (152) substrates through the formation of the iminium intermediate (155) and electrostatic activation (156). The resulting (g) trisubstituted cyclopropanes (157) were obtained with high levels of enantio- and diastereo-control.180... 

Indoline-2-carboxylic acid /9S767-06-7/M 163.2, m 177"(dec), [a] +11.0" (c 0.3, MeOH)- Purify it as for the S-enantiomer below. The R-(+)-hydrochloride has [172152-19-1]. It is a proline based oiganocatalyst which promotes the enantioseleetive formation of cyclopropanes by reaction between 2-(dimethyl-X -sulfanylidene)-l-phenyl-ethanone (for stable sulfonium ylides see Ratts Yao J Org Chem 31 1185 1966) and but-2-enals in high yields and very high stereoselectivity involving Direct Electrostatic Activation (DEA) [Kunz Mac Millan JA/w Chem Soc 127 3240 2005.]... 

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