# Ring Enlargements of in Situ-Formed Cyclopropanones by Sulfoxonium Ylides: One-Pot Synthesis of Alkylidene Cyclobutanones

## TL;DR

A new one-pot method is developed to efficiently synthesize alkylidene cyclobutanones from cyclopropanone surrogates using sulfoxonium ylides.

## Contribution

The study introduces a stereoselective one-pot synthesis of alkylidenecyclobutanones with up to 84% yield using sulfoxonium ylides.

## Key findings

- Sulfoxonium ylides react with cyclopropanone surrogates to form four-membered rings in up to 84% yield.
- The stereochemical outcome depends on substituents: alkyl groups retain configuration, while aryl groups reduce enantiopurity.
- Mechanistic studies suggest nucleophilic attack followed by ring enlargement as the key steps.

## Abstract

A one-pot method
for the stereoselective synthesis of alkylidenecyclobutanones
from cyclopropanone surrogates is reported. Reaction partners are
stable sulfoxonium ylides, leading to the four-membered rings in up
to 84% yield. Mechanistic studies indicate that the transformation
proceeds via nucleophilic attack of the sulfoxonium ylide on the three-membered
ring, followed by ring enlargement. The stereochemical outcome of
the ring expansion is substituent-dependent: alkyl groups promote
complete retention of configuration, whereas aryl groups result in
partial erosion of enantiopurity.