# Chiral Isochalcogenourea‐Catalysed Enantioselective (4+2) Cycloadditions of Allenoates

## TL;DR

This paper introduces a new method using chiral isochalcogenoureas to control the stereochemistry of allenoate reactions with high selectivity and efficiency.

## Contribution

The first use of chiral isochalcogenoureas for enantioselective (4+2) cycloadditions of allenoates is demonstrated.

## Key findings

- Chiral isochalcogenoureas enable high enantioselectivity and diastereoselectivity in allenoate cycloadditions.
- The new method provides good reaction yields and novel stereoselective pathways.
- The factors influencing enantioselectivity are explained and compared to other Lewis bases.

## Abstract

Allenoates are versatile building blocks which are primarily activated and controlled using chiral tert. phosphine and tert. amine Lewis bases. We herein report the first example of allenoate activation by using chiral isochalcogenoureas (IChU) for formal (4+2) cycloaddition reactions. Compared to established phosphine and amine catalysis, the use of these easily available Lewis bases enables new stereoselective reaction pathways proceeding with high enantioselectivities, diastereoselectivities, and in good yields. In addition, the factors governing enantioselectivity and the origin of the observed differences compared to other commonly used Lewis bases are explained.