Controlled Synthesis of alpha-Allenic Ester and Spiro Ketone Derivatives from Tailored alpha-Substituted Cycloalkanones Through Cascade Reactions:Exploring the Possible Reaction Pathways by Means of Semiempirical MO Calculations

摘要

Functionalized bicyclic electrophilic allenes and (or) spiro ketones have been obtained through a cascade reaction when acetylenic omega-keto esters were treated with tetra-n-bu-tylammonium fluoride (TBAF).The isolated products can be modulated by using different starting materials (i.e.varying ring size,spacer length) and reaction times.The results indicate that these reactions take place under kinetic control.In line with this,a Semiempirical study was carried out in order to determine the preferred reaction pathways and the preferred cis/trans conformation of the bicyclic allenic derivatives.An excellent correlation was found between theoretical and experimental results,and the whole process dramatically depends on the presence of the HF molecule.