Synthesis of polycyclic cyclobutane derivatives by tandem intramolecular Michael-aldol reaction under two complementary conditions: TBDMSOTf-Et3N and TMSI-(TMS)2NH

Article abstract of DOI:10.1021/ja00071a024

The treatment of αβ-unsaturated esters having a ketone function at an appropriate position with either TBDMSOTf in the presence of Et₃N or TMSI in the presence of (TMS)₂NH provided, via a tandem intramolecular Michael-aldol reaction sequence, several different types of cyclobutane derivatives. The two reaction conditions were complementary. Tricyclo[4.2.1.0^3,8]nonanes 34 and 55, tricyclo[5.1.10^4,8]nonane 40, tricyclo[5.4.0.0^3,7]undecane 51, tetracyclo[5.4.0.0^3,7.0^9,11]undecane 45, and the bicyclo[3.2.0]heptanes 56, 57, and 58, which have structures either partially or completely similar to those of endiandric acids A (1a), B (1b), and C (2), trihydroxydecipiadiene (3), lintenone (4), italicene (5), and filifolone (6), were stereoselectively synthesized by the tandem reaction.