Richard H. Wallace

Preparation and 1-carbon homologation of boronic ester substituted Δ2-isoxazolines: The 1,3 dipolar cycloaddition of nitrile oxides to vinyl boronic esters

Abstract The dipolar cycloaddition of a variety of nitrile oxides to pinacol vinylboronate ( 2 ) is described. In addition, the 1-carbon homologation of the boronic ester substituted Δ 2 -isoxazolines obtained from the cycloadditions has been carried out employing iodomethyllithium.

An efficient method for the preparation of optically active 4-hydroxy-Δ2-isoxazolines

Abstract In this letter we report a method for the preparation of optically active 4-hydroxy-Δ 2 -isoxazolines. This methodology relies on the use of a camphorsultam substituted vinylboronic ester which upon nitrile oxide cycloaddition and oxidation affords the optically active 4-hydroxy-Δ 2 -isoxazolines in good yield.

Sodium percarbonate: A multifunctional reagent for the preparation of optically active 4-hydroxy-Δ2-isoxazolines

Abstract In this letter we report a general method for the preparation of optically active 4-hydroxy-Δ2-isoxazolines. This one-pot method employs sodium percarbonate for nitrile oxide generation, oxidation of the intermediate boronic ester substituted Δ2-isoxazoline, and cleavage of the chiral auxiliary from the final product.

A facile method for the preparation of 4-hydroxy-Δ2-isoxazolines via a cycloaddition/oxidation procedure employing nitrile oxides and vinylboronic esters

Abstract The 1,3-dipolar cycloaddition of aromatic nitrile oxides with trans-1,2-disubstituted vinylboronic esters affords the 4-boronic ester substituted Δ2-isoxazoline as the major regioisomer. If the reaction mixture is treated with t-BuOOH the corresponding 4-hydroxy-Δ2-isoxazolines are obtained in good yield.

The preparation of optically active boronic ester substituted Δ2-isoxazolines

Abstract In this paper we report our recent results in the area of nitrile oxide cycloaddition to optically active vinylboronic esters to afford optically active boronic ester substituted Δ 2 -isoxazolines. In these studies, a number of optically active diols were investigated and TADDOLs have been found to afford the best diastereoselectivity. The mixture of diastereomers obtained in these reactions can be readily purified by formation of the diethanolamine–boron complexes and recrystallized to afford the pure enantiomers.

Dimeric products from the dissolving metal reduction of camphor

Abstract Various dissolving metal reductions of (+)-camphor afford one of two pinacols frequently accompanied by a dimeric product in which one bicycloheptane unit has been cleaved. Similar reductions of (±)-camphor afford various mixtures of (±)- exo - endo , (±)- endo - endo and meso endo - endo pinacols. The structures of two of these products were confirmed by X-ray crystallography.

Dissolving metal reductions of ketones: comments on the dianion mechanism

Abstract The reduction of (+)-camphor using Li, Na, and K in THF with sonication is reported. These reductions give the same results as those obtained in NH 3 . The mechanism of these reactions is discussed.

The In Situ Generation and Use of Iodomethyllithium for the One-Carbon Homologation of Boronic Esters and Epoxide Formation from Carbonyl Compounds

Abstract Iodomethyllithium is shown to be an effective reagent for the one-carbon homologation of oxygenated boronic esters. The use of iodomethyllithium for the preparation of pinacol iodomethaneboronate and for the synthesis of epoxides from carbonyl compounds is also discussed.

A Quick and Easy Simplification of Benzocaine's NMR Spectrum

The preparation of benzocaine is a common experiment used in sophomore-level organic chemistry. Its straightforward procedure and predictable good yields make it ideal for the beginning organic student. Analysis of the product via NMR spectroscopy, however, can be confusing to the novice interpreter. An inexpensive, quick, and effective method for simplifying the NMR spectrum is reported. The method results in a spectrum that is cleanly integrated and more easily interpreted.