Recent developments in the stereoselective synthesis of α-aminoacids

https://chemistry.mdma.ch/hiveboard/rhodium/pdf/nef.reaction.review.2004.pdf

Recent synthetic developments in the nitro to carbonyl conversion (Nef reaction)

Recent Progress of the Synthetic Studies of Biologically Active Marine Cyclic Peptides and Depsipeptides

This review focuses upon the preparation and reactions of nitroalkenes that are substituted with a heteroatom group at C-1 of the alkene unit. Derivatives of β-nitroenamines and related species are not included

Heterosubstituted nitroalkenes in synthesis

The Balz-Schiemann synthesis of aryl fluorides via the thermal decomposition of aryl diazonium tetrafluoroborate salts represents both the earliest and the most proverbial example of the BF4 ion as a nucleophilic fluoride source. Mechanistic studies of the Balz-Schiemann reaction have accrued strong experimental support for an SN1 mechanism via the intermediacy of an aryl cation, which is quenched by fluoride transfer directly from the BF4 ion. A notable advance in this area has been the development by Ohmori and co-workers of a fluorinative variant of the Mitsunobu reaction, involving the electrooxidative generation and subsequent thermal decomposition of alkoxytriphenylphosphonium tetrafluoroborates, allowing for the conversion of alcohols to the corresponding alkyl fluorides with inversion of configuration. Although stereoselectivity during C-F bond formation for reactions proceeding via (putative) carbocation intermediates can be highly variable, the ring-opening of strained rings or ?iranium intermediates via fluoride transfer from fluoroborate ions typically proceeds with high stereoselectivity.

Beyond the Balz-Schiemann reaction: the utility of tetrafluoroborates and boron trifluoride as nucleophilic fluoride sources.

A new method for the preparation of tertiary butyl ethers and esters

Preparation of α-substituted S-phenylthio esters from 2-nitro-2-phenylthio oxiranes

Epoxidation of the 1-nitro-1-(p-tolylthio)alkene 1 derived from D-isopropylideneglyceraldehyde with lithium tert-butyl peroxide affords the syn epoxide 2 with moderate selectivity, whereas epoxidation with potassium tert-butyl peroxide affords the anti diastereoisomer 3 preferentially; treatment of each of the epoxides 2 and 3 with amines, including ammonia, gives diastereoisomerically pure α-amino thioesters with no trace of stereoisomeric contamination.

Control of diastereoselectivity in the nucleophilic epoxidation of 1-arylthro-1-nitroalkenes: synthesis of diastereoisomerically pure γ-hydroxy threonine derivatives

T-butyl 2,2,2-trichloroacetimidate (1), readily prepared by addition of t-butanol to trichloroacetonitrile, is an efficient reagent for the preparation of t-butyl ethers and esters in the presence of a catalytic amount of boron trifluoride etherate.

A New Method for the Preparation of Tertiary Butyl Ethers and Esters.

2-Nitro-2-phenylthio oxiranes (3), prepared by nucleophilic epoxidation of 1-nitro-1-phenylthio alkenes (1), react with a variety of heteroatomic nucleophiles to give α-substituted S-phenylthio esters (2). Of special note is the efficient reaction of 2-nitro-2-phenylthio oxiranes with boron trifluoride etherate in toluene at room temperature to give α-fluoro S-phenylthio esters (8).

Joanna M. Kirk

Papers

A new method for the preparation of tertiary butyl ethers and esters

Preparation of α-substituted S-phenylthio esters from 2-nitro-2-phenylthio oxiranes

Control of diastereoselectivity in the nucleophilic epoxidation of 1-arylthro-1-nitroalkenes: synthesis of diastereoisomerically pure γ-hydroxy threonine derivatives

A New Method for the Preparation of Tertiary Butyl Ethers and Esters.

Preparation of α-Substituted S-Phenylthio Esters from 2-Nitro-2- phenylthio Oxiranes.