# Conformational studies of biaryl-bridged seven-membered lactones with a quaternary carbon center

## TL;DR

This paper studies the preferred shapes of a specific type of seven-membered lactone molecule, finding that larger groups prefer axial positions.

## Contribution

The study reveals a novel conformational preference in biaryl-bridged seven-membered lactones with a quaternary carbon center.

## Key findings

- Larger substituents prefer axial positions in the stable conformers of the lactone molecules.
- Crystal structures and DFT calculations explain the conformational selectivity based on substituent volume.
- The observed conformational preference is consistent across the studied series of compounds.

## Abstract

We show the synthesis and conformational studies of a series of 7,7-disubstituted-dibenzo[b,d]oxepin-6(7H)-ones that feature biaryl-bridged seven-membered lactones with a quaternary carbon center, in which the larger substituents prefer the axial positions. Further studies on the crystal structures and DFT calculations revealed that the high selectivity observed is attributed to the volume of substituents.

Here, conformations of a series of 7,7-disubstituted-dibenzo[b,d]oxepin-6(7H)-ones were studied and we found that the stable conformers all favor to place the larger group in the axial position instead of the equatorial position.