Halogenation asymmetric catalysis

The 1/BQ system alone or with Lewis acid additives was also employed for asymmetric catalysis in the synthesis of /3-amino acids235. During an elaboration of the tandem catalytic asymmetric chlorination/esterification process, Lectka and coworkers found that proton sponge 1 competes with ketenes in the reaction with halogenating agents, such... 

AgOTf CH2CI2, -56°C,2h cases, see Table 2) - tolerent to halogen, alkoxy, N(Ts)2, OC(0)R, CO2R - works with propene (-15 °C) and other vinylarenes - amenable to asymmetric catalysis ... 

Recent Developments in Catalytic, Asymmetric a-Halogenation A New Frontier in Asymmetric Catalysis France, S. Weatherwax, A. Lectka, T. Eur. J. Org. Chem. 2005, 475. 

This compilation embraces a wide variety of subjects, such as solid-phase and microwave stereoselective synthesis asymmetric phase-transfer asymmetric catalysis and application of chiral auxiliaries and microreactor technology stereoselective reduction and oxidation methods stereoselective additions cyclizations metatheses and different types of rearrangements asymmetric transition-metal-catalyzed, organocatalyzed, and biocatalytic reactions methods for the formation of carbon-heteroatom and heteroatom-heteroatom bonds like asymmetric hydroamina-tion and reductive amination, carboamination and alkylative cyclization, cycloadditions with carbon-heteroatom bond formation, and stereoselective halogenations and methods for the formation of carbon-sulfur and carbon-phosphorus bonds, asymmetric sulfoxidation, and so on. 

Enantioselective -Functionalization of Aldehydes and Ketones The direct and enantiosective functionalization of enolates or enolate equivalents with carbon-, nitrogen-, oxygen-, sulfur- or halogen-centered electrophiles represents a powerful transformation of chemical synthesis and of fundamental importance to modem practitioners of asymmetric molecule constmction. Independent studies from List, J0rgensen, Cordova, Hayashi, and MacMiUan have demonstrated the power of enamine catalysis, developing catalytic enantioselective reactions such as... 

A range of nitrogen, phosphorus, chalcogen (O, S, Se) and halogen electrophiles react with enamines, resulting in a net a-functionalization of the carbonyl compound. In the past five years, all of these reaction variants have been subjected to asymmetric enamine catalysis, with excellent results. 

Two examples of cyclization strategies leading to C3 quatemized oxindoles in the absence of asymmetric control have been disclosed by Klumpp and coworkers (aryl substitution at C3) [38] and the Ackerman group (alkyl and aryl substitution at C3 of 4-azaoxindoles) [39]. A direct carbon-carbon coupling of an anilide (i.e., no orf/jo-halogen) in racemic form has been reported by Perry and Taylor who employed Pd-catalysis with Cu(OAc)2 as the oxidant [40]. 

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