# [3+2] Cycloaddition to a Chiral 5-Methylene-1,3-dioxolan-4-one and Pyrolysis of the Spiro Adducts

## TL;DR

This paper studies chemical reactions involving a chiral compound derived from lactic acid and explores the outcomes of pyrolysis of the resulting adducts.

## Contribution

The study presents new [3+2] cycloaddition reactions and novel gas-phase pyrolysis pathways for a chiral dioxolanone derivative.

## Key findings

- Spiro adducts were successfully formed with benzonitrile oxide, acetonitrile oxide, diazomethane, and diphenyldiazomethane.
- Pyrolysis of the adducts led to diverse products, including pivalaldehyde, CO2, and benzophenone.
- Failed attempts with nitrile sulfide, nitrile imine, and azides highlight selectivity in the reaction conditions.

## Abstract

The [3+2] cycloaddition chemistry of (2S)-5-methylene-2-t-butyl-1,3-dioxolan-4-one, derived from lactic acid, has been examined, and spiro adducts have been obtained with benzonitrile oxide, acetonitrile oxide, diazomethane and diphenyldiazomethane. The structure and absolute stereochemistry of the benzonitrile oxide adduct has been confirmed by X-ray diffraction, and all the adducts have been fully characterised by 1H and 13C NMR. Attempted cycloaddition with a nitrile sulfide, a nitrile imine and azides failed. Pyrolysis results in a range of novel gas-phase reactions, with the nitrile oxide adducts giving pivalaldehyde, CO2, the nitrile and ketene, the diazomethane adduct losing only N2 to give a cyclopropane-fused dioxolanone, and the diphenylcyclopropane derived from diphenyldiazomethane giving mainly benzophenone in a sequence involving the loss of pivalaldehyde and methyleneketene.