Conjugated 1,8 and 1,6 Addition of Bis<i>-</i>Trimethylsilylketene Acetal to Activated <i>p</i>-Quinone Methides via Trifluoromethanesulfonic Anhydride

In this work, we studied the conjugated additions of bis-trimethylsilylacetalketene acetals (bis-TMSKA) to <i>para</i>-quinone methides (<i>p</i>-QMs), which are one of the most explored molecules for the study of conjugated additions and gained significant attention in organic chemistry due to their versatile reactivity, particularly in Michael addition reactions. In this study, trifluoromethanesulfonic anhydride (Tf₂O) was used as an activating agent for <i>p</i>-QMs, aiming to achieve 1,6-Michael addition products and the least reported 1,8-Michael addition with pyridine substituents. The reactivity of <i>p</i>-QMs derived from pyridine demonstrated distinct reaction pathways, leading to the formation of δ and γ lactones. The investigation also involved synthesizing a 1-indanone derived from the carboxylic acids obtained from the 1,6-addition.