Stereocontrolled Fluorobenzylation of Vinyl Sulfones and α,β-Unsaturated Esters Mediated by a Remote Sulfinyl Group. Synthesis of Functionalized Enantiomerically Pure Benzylic Fluorides

Alkylation and silylation of α-fluorobenzyl anion intermediates

Simple α-fluorobenzyl anions reacted with electrophiles such as non-activated alkyl halides and chlorotrimethylsilane. Upon treatment with LTMP as the base, fluoromethylbenzenes took part in the formation of α-monofluorobenzyl anions without stabilizing o-substituents. Furthermore, the resulting α-silyl fluoromethylbenzenes reacted with electrophiles such as acetophenone and benzaldehyde in the presence of cesium fluoride to form α-fluorobenzylated alcohols.

Asymmetric [2,3]-Wittig Rearrangement: Synthesis of Homoallylic, Allenylic, and Enynyl α-Benzyl Alcohols

A highly stereoselective [2,3]-Wittig rearrangement of allylic and propargylic ethers controlled by a chiral sulfoxide moiety is presented. The activation provided by the sulfoxide at the remote ortho position allows the rearrangement of less-activated and unexplored benzylic carbanions. Thus, this general methodology gives access to the asymmetric synthesis of homoallylic, enynyl, and allenylic α-benzyl alcohol derivatives.

C-H Coupling Reactions Directed by Sulfoxides: Teaching an Old Functional Group New Tricks

Sulfoxides are classical functional groups for directing the stoichiometric metalation and functionalization of C-H bonds. In recent times, sulfoxides have been given a new lease on life owing to the development of modern synthetic methods that have arisen because of their unique reactivity. They have recently been used in catalytic C-H activation proceeding via coordination of an internal sulfoxide to a metal or through the action of an external sulfoxide ligand. Furthermore, sulfoxides are able to capture nucleophiles and electrophiles to give sulfonium salts, which subsequently enable the formation of C-C bonds at the expense of C-H bonds. This Review summarizes a renaissance period in the application of sulfoxides arising from their versatility in directing C-H functionalization.

Stereoselective nucleophilic fluoromethylation of aryl ketones: dynamic kinetic resolution of chiral α-fluoro carbanions

Although many methods are available for the synthesis of optically enriched monofluoromethyl secondary alcohols, synthesizing optically enriched monofluoromethyl tertiary alcohols remains a challenge. An efficient and easy-to-handle nucleophilic fluoromethylation protocol was developed. The current monofluoromethylation showed much higher facial selectivity than the corresponding difluoromethylation and proceeded via a different type of transition state. Excellent stereoselective control at the fluorinated carbon chiral center was found, an effect believed to be facilitated by the dynamic kinetic resolution of the chiral α-fluoro carbanions.

Use of lithiated chiral o-sulfinylbenzyl carbanions for the one-pot building of linear fragments containing up to four connected stereocenters

The reaction of o-sulfinylbenzyl carbanions with prochiral Michael acceptors, such as differently sized cycloalkenones, proceeded with high levels of stereoselectivity, generating molecules containing up to three asymmetric carbon centers in just one synthetic step. All these reactions involved the use of either a proton or an acylating reagent as the final electrophile. Furthermore, the trapping of the enolate resulting from Michael addition with prochiral electrophiles, such as aldehydes or N-sulfonylimines, allowed the highly stereoselective synthesis of densely functionalized compounds containing four chiral centers in just a one-pot sequence, the stereochemical outcome of the sequence being controlled by the sulfinyl auxiliary.