Brønsted-Acid-Catalyzed Synthesis of 3-Alkoxy and 3-Sulfamido Indanones via a Tandem Cyclization

Abstract

Brønsted-acid-catalyzed allylic substitution reactions of the in situ generated 3-hydroxy indanones with alcohols and sulfamides were investigated, which provided a facile route for the synthesis of a large variety of 3-alkoxy and 3-sulfamido indanones. The key intermediates, 3-hydroxy indanones, were obtained through the intramolecular Meyer−Schuster rearrangement of o-propargyl alcohol benzaldehydes. The resulting 3-benzyloxy indanone could be selectively modified by allylic sulfonamidation and reduction reactions.

Recent Developments in the Meyer‐Schuster Rearrangement

“…In the presence of para ‐toluene sulfonic acid, the propargylic alcohols 120 having an aldehyde in ortho position underwent the MSR and the intermediate allenol reacted intramolecularly with the vicinal aldehyde to get the intermediate 3‐hydroxy indanone 121 . Then reactions with various types of alcohols, or sulfamides, afforded the target molecules 122 and 123 , respectively in fair to good yields [76] …”

“…Then reactions with various types of alcohols, or sulfamides, afforded the target molecules and 123, respectively in fair to good yields. [76] The MSR has been used to prepare naphthols and photochromic naphtopyrans as indicated in Scheme 29. [77a,b] In the presence of trifluoroacetic acid, the MSR performed from the easily available propargylic alcohols 124 gave the enones 125 as the Z isomers.…”

Transition‐Metal‐Free Synthesis of 1‐Indanone Skeleton: A Brief Update

“…p ‐TsOH is an important cost‐effective reagent often used as Brønsted acid catalyst in various organic synthesis. Recently, Zhou and Zhu group realized a p ‐TsOH catalyzed allylic alkoxylation and sulfonamidation reactions for the synthesis of 3‐alkoxy and 3‐sulfamido indanones 20 / 22 [32] . The key intermediates, 3‐hydroxyindanones 18 are obtained through the intramolecular Meyer‐Schuster rearrangement of readily available ortho ‐propargyl alcohol benzaldehydes 17 (Scheme 6).…”

Facile synthesis of the spiro-pyridoindolone scaffoldviaa gold-catalysed intramolecular alkynol cyclisation/hydroindolylation

“…In this context, we envisioned that with the simple alkynol substrate 1 without an annulated benzene ring in the chain, the gold-catalysed cyclisation should exclusively result in spiro-pyridoindolone 2 , as the formation of the carbocation is not as facile as in the former case. 10 This has been planned in the context of developing simple methods for the synthesis of a pyridoindolone skeleton, which is a privileged structural unit present in numerous alkaloids and investigational drugs (Fig. 1).…”