The acyloin reaction using tethered diesters

Abstract

A study of the intramolecular acyloin condensation using diesters tethered by their alkoxide groups was undertaken. The goal was to provide a method for optimizing the yield of mixed acyloin products from the reaction of two different esters by utilizing tethered dissimilar esters as substrates. The results of the study show that the yield of the acyloin condensation is dependant on the tether length. Tethers of 8 and 14 carbons in length give yields comparable to those obtained from an intermolecular control reaction while shorter tethers give reduced yields of product. However, the use of mixed tethered diesters and a crossover experiment between two different tethered substrates provides a statistical distribution of products. These observations have been interpreted as resulting from a fragmentation of the initially formed radical anion intermediate that destroys the tethered nature of the substrate(s).

New Coupling Reactions of Some Acyl Chlorides with Samarium Diiodide in the Presence of Samarium: Carbinols from Three Acyl Units

“…[41] Fraction III: 6-Hydroxy-7-dodecanone (8) (0.076 g, 0.4 mmol, 6%). [42] Fraction IV: Hexanoic acid (25) (0.059 g, 0.8 mmol, 7%). [39] Treatment of Stearoyl Chloride (26) with SmI 2 /Sm: Anhydrous NiI 2 (0.015 g, 0.05 mmol) was added to a solution of SmI 2 , which had been obtained from samarium (0.827 g, 5.50 mmol) and diiodomethane (0.652 g, 2.50 mmol) in THP (10 mL).…”

Exerting control over the acyloin reaction

“…In 1993, Hutchinson et al subjected tethered diesters, joined through the ester oxygen atoms by a linker, to heterogeneous reductive conditions and furnished an almost statistical mixture of possible acyloin products. 5 Herein, we describe a method for conducting the acyloin reaction under low temperature conditions and the introduction of a linker between two different ester oxygen atoms that allows crossed acyloin reactions to proceed with high selectivity.…”

“…Therefore, we turned to the use of a tether between the two ester components, searching for an intramolecular, and therefore controlled, acyloin coupling. Aware of previous (and unsuccessful) attempts to achieve such a transformation, 5 we briefly examined the reactions of unsymmetrical diesters of ethylene glycol, but did not uncover significant levels of selectivity. However, the placement of a more rigid norbonyl-diol unit between two esters showed promise and was investigated further.…”