Exploring the Unconventional Re-activity of Alkynes and Propargylic alcohols
Propargylic alcohols are one of the most useful building blocks available to the synthetic chemists, which possess two functional groups. Among the various useful reactions of propargylic alcohols, the Meyer–Schuster rearrangement to enones is a transformation of significant synthetic potential that has been widely exploited in organic synthesis. This rearrangement involves an isomerization of a propargylic alcohol to form a 1,3-transposed allenol followed by its enol-keto tautomeric protonation at the central carbon atom to form the enone product. Recently, few research groups have developed an intercepted Meyer–Schuster rearrangement to broaden the utility of this classical process in synthetic organic chemistry. Accordingly, the key protonation step was replaced by the reaction of the allenol 2 with an electrophile (E+), to generate a-functionalized complex enones.
In contrast to the known electrophilic interception methodologies, we have designed a conceptually novel strategy, i.e., nucleophilic interception of the M-S intermediate an allenol. To achieve this goal, it was necessary to alter the electronic properties of the allenol from being nucleophilic (as in classical M-S rearrangement) to an electrophilic, so that nucleophiles can easily be added. This approach provided us an opportunity to uncover; unconventional modes of reactivity of propargylic alcohols.
To convert the nucleophilic allenol into an electrophilic species, we have chosen an intramolecular nucleophilic assistance strategy.This cis-enoate assisted, nucleophilic intercepted M-S rearrangement strategy was well demonstrated primarily by employing neutral aromatics as secondary nucleophiles, for a novel, metal free, alpha-arylation process for the efficient synthesis of complex conjugated enone systems.
Development of New Cascade reactions based Synthetic Methodologies and Total Synthesis of Bioactive Natural Products and Drugs
The architecturally interesting and bioactive molecules are the driving force behind the development of new strategies in synthetic organic chemistry. In nature the biosynthesis of natural products involves the conversion of simple and small starting materials to structurally complex molecules through a series of highly controlled cascade reactions, catalyzed by transformation-specific enzymes.This biosynthesis in nature provides an interesting and alternative strategy to the traditional single-target approaches, since it typically involves the construction of a group of natural products through a common intermediate. This concept is commonly called as collective synthesis. Having inspired by the Nature, in our laboratory we aim to develop cascade strategies that allow the transformation of readily available and easily accessible precursors into multifunctional polycyclic intermediates which will be useful for the synthesis of bioactive target molecules in a rapid and efficient manner.