10.1016/0040-4020(80)88028-8
The research focuses on the pericyclic transformations of tetracyclo[8,2,1,02'9]trideca-4,6,11-trienes, exploring the synthesis and properties of homologous and related polycyclic systems with unsaturated rings fused syn and anti to the cyclobutane moiety. The study aims to understand the thermal intramolecular [4+2] cycloaddition in substituted cyclooctatrienes, leading to the formation of dihydrosemibullvalene derivatives through a novel sequence involving cheletropic loss of carbon monoxide and electrocyclic ring opening. The conclusions drawn from the research highlight the potential for these compounds to undergo various pericyclic transformations, such as electrocyclic ring-opening and closure, and sigmatropic group transfer, which are competitive processes when steric inhibition is not severe.
10.1039/c3sc50643f
The study presents a method for synthesizing cyclobutane lignans and their analogs using photoinduced electron transfer. Key chemicals include oxygenated alkenes, which are used to form terminal or substituted cyclobutane adducts with complete regiocontrol and trans stereochemistry. The aromatic electron relay (ER), such as anthracene or naphthalene, is crucial for minimizing competing cycloreversion. The photooxidant 2,4,6-tris(4-methoxyphenyl)pyrylium tetrafluoroborate (p-OMeTPT) is used to excite the system and facilitate the oxidation of the alkene substrate by the ER, which then forms a cation radical capable of oxidizing the alkene. This method has been successfully applied to synthesize natural products like magnosalin and pellucidin A. The study also explores the role of the ER in preventing cycloreversion and polymerization, highlighting its importance in achieving higher yields and selectivity in the cyclobutane synthesis.
