Stereospecific formation of 1,2-dioxetanes from cis- and trans-diethoxyethylenes by singlet oxygen

TLDR: In this paper, a solution of lithium bis(trimethylsilyl)amide in tetrahydrofuran (25 ml of a 1.0 M solution) was injected and the flask immersed in a Dry Ice-acetone bath.

Abstract: not only gives much higher yields than the usual Reformatsky procedure but is much less time consuming as indicated by the following procedure for the conversion of cinnamaldehyde into II. A dry 100-ml flask equipped with septum inlet and magnetic stirrer was flushed with nitrogen. A solution of lithium bis(trimethylsilyl)amide in tetrahydrofuran (25 ml of a 1.0 M solution) was injected and the flask immersed in a Dry Ice-acetone bath. Ethyl acetate (2.42 ml, 25 mmol) was added dropwise over a period of 2 min and the solution was stirred for an additional 15 min to complete the formation of I. Cinnamaldehyde (2.95 ml, 25 mmol) was then injected and after 5 min the solution was hydrolyzed by injection of 5 ml of 20 % hydrochloric acid. The solution was allowed to reach room temperature. Addition of pentane to the separated organic phase followed by cooling gave 5.17 g (94% yield) of ethyl-3-hydroxy-5-phenyl-4-pentanoate, II, mp 38-39 °. We are presently exploring in greater detail the synthetic uses of lithio ethyl acetate. In addition, we are