Alkylation

About: Alkylation is a research topic. Over the lifetime, 29915 publications have been published within this topic receiving 464944 citations. The topic is also known as: alkylation reaction.

Homologation and Alkylation of Boronic Esters and Boranes by 1,2-Metallate Rearrangement of Boron Ate Complexes

Abstract: Organoboranes and boronic esters readily undergo nucleophilic addition, and if the nucleophile also bears an α-leaving group, 1,2-metallate rearrangement of the ate complex results. Through such a process a carbon chain can be extended, usually with high stereocontrol and this is the focus of this review. A chiral boronic ester (substrate control) can be used for stereocontrolled homologations with (dichloromethyl)lithium in the presence of ZnCl2. Subsequent alkylation by an organometallic reagent also occurs with high levels of stereocontrol. Chiral lithiated carbanions (reagent control) can also be used for the reaction sequence with achiral boronic esters and boranes. Aryl-stabilized sulfur ylide derived chiral carbanions can be homologated with a range of boranes including vinyl boranes in good yield and high diastereo- and enantioselectivity. Lithiated alkyl chlorides react with boronic esters, again with high stereocontrol, but both sets of reactions are limited in scope. Chiral lithiated carbamates show the greatest substrate scope and react with both boronic esters and boranes with excellent enantioselectivity. Furthermore, iterative homologation with chiral lithiated carbamates allows carbon chains to be "grown" with control over relative and absolute ste- reochemistry. The factors responsible for stereocontrol are discussed. © 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 9: 24-39; 2009: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20168

Catalytic alkylation of methyl-N-heteroaromatics with alcohols.

Abstract: A novel catalytic C-C coupling reaction in which N-heteroaromatic-substituted methyl groups are efficiently alkylated using primary alcohols is introduced. The synthesis protocol is based on iridium catalysts and most likely relies on the "borrowing hydrogen" or "hydrogen autotransfer" mechanism. A variety of substrate combinations can readily be employed in this reaction, including pyrimidines, pyrazines, pyridazines, and even fairly activated 2- and 4-picolines.

Alkylation, arylation, and vinylation of acyl chlorides by means of organotin compounds in the presence of catalytic amounts of tetrakis(triphenylphosphine)palladium(o)

Abstract: Alkylation, arylation, and vinylation of acyl chlorides by means of organotin compounds in the presence of catalytic amounts of tetrakis(triphenylphosphine)palladium(O) were demonstrated. The corresponding ketons were obtained in fairly good yields.

Enantioselective alkylation of carbonyl compounds. From stoichiometric to catalytic asymmetric induction

Abstract: Multinuclear organometallic species play a significant role in alkylation of carbonyl compounds. Enantioselective alkylation of aldehydes using a 1: 1 reagent/substrate stoichiometry is achievable by chirally modified lithium/magnesium binary organometallic reagents. For example, diethylmagnesium treated with di-O-lithio-(S)-2.2'- dihydroxy- 1, 1'-binaphthyl reacts with benzaldehyde in a THF- dimethoxyethane mixture at -100 OC to give (S)- 1-phenyl- 1- propanol in 92% ee. In the presence of a catalytic quantity of (4-3- exo-(dimethy1amino)isoborneol (DAIB), reaction of dialkylzincs and aldehydes in nonpolar media is accelerated greatly to lead to the corresponding S alcohols in very high enantiomeric excesses (up to 99% ee). The enantioselective catalysis involves fluxional organozinc species and the product-forming dinuclear intermediate possesses DAIB auxiliary, an aldehyde ligand, and three alkyl groups, where it is the bridging alkyl group, rather than the terminal alkyls, that migrates from zinc to the carbonyl carbon.