Expanding the Chemical Space of 1,2-Difunctionalized Cyclobutanes.

An efficient approach to the synthesis of previously unavailable or hardly accessible 1,2-difunctionalized cyclobutanes (mostly with NH/NHBoc, OH, SH, or SOF groups attached to the carbocycle either directly or via a CH unit) relying on the divergent strategy is described. This class of compounds provides -enriched and conformationally restricted building blocks that are of special demand for medicinal chemistry. The target compounds were prepared not only as pure racemic (±)-- and (±)--diastereomers but in some cases also as single enantiomers.