Activation of o-Propargyl Alcohol Benzaldehydes under Acetalization Conditions for Intramolecular Electrophile Intercepted Meyer–Schuster Rearrangement

Abstract

The reactivity of o-propargyl alcohol benzaldehydes has been increased tremendously toward Brønsted acid-catalyzed intramolecular electrophile intercepted Meyer–Schuster (M–S) rearrangement under acetalization conditions using trimethyl orthoformate (TMOF). The in situ formed acetal transfers the methoxy group intramolecularly to generate the M–S intermediate in even less reactive substrates, and the formed oxocarbenium ion makes the carbonyl more electrophilic for an effective intramolecular trapping of the M–S intermediate to furnish the indanone derivatives.

A TfOH‐Catalyzed Multicomponent Reaction of Propargylic Alcohols, Sulfonamides and Aldehydes for the Synthesis of Acyclic α‐Arylidene β‐Aminoketones

“…Our previous studies indicated that only primary 3‐aryl propargyl alcohols underwent one‐pot multi‐step transformations smoothly, beginning with the Meyer‐Schuster rearrangement [10,12,13] . Very recently, the intramolecular electrophile intercepted Meyer‐Schuster rearrangements of secondary and tertiary o‐propargyl alcohol benzaldehydes have been reported [2l,14] . On this basis, the present work examined the reactions of sterically‐hindered 3‐phenyl propargyl alcohols with either one or two −CH 3 groups or one or two Ph groups α to the −OH (Table 4).…”

Synthesis of Diverse Allylic Sulfone Derivatives via Sequential Hydroalkoxylation of 1,3‐Enynes

“…The intermediate 1 ab so formed after the typical TMS deprotection yields intermediate 1 ac . The electrophilic oxocarbenium cation generated within intermediate 1 ac is highly susceptible to nucleophilic attack from another methoxide ion, [13] ultimately resulting in the formation of the desired product 2 a .…”