A Concise Domino Synthesis of Benzo‐1,4‐heterocycle Compounds via a Piancatelli/C–N Coupling/Michael Addition Process Promoted by La(OTf)₃

Abstract

A La(OTf)3‐catalyzed domino method has been developed to synthesize the cis‐1,4‐benzoxazine derivatives from 2‐furylcarbinols 1 and o‐aminophenol derivatives, by a Piancatelli/C–N coupling/Michael addition process. A wide array of substrates could be used to give the desired products in good yields. Since this method involves simple reaction conditions and short reaction times, and has a broad substrate scope, it is particularly attractive for the efficient development of libraries of biologically relevant 1,4‐benzoxazine derivatives. Furthermore, a similar strategy was also successfully applied to form 1,2,3,4‐tetrahydroquinoxaline derivatives from 1 and N‐substituted o‐diaminobenzenes.

Synthesis and Applications of Stenhouse Salts and Derivatives

“…The reaction of tosyl‐ or mesityl‐monoprotected diamines selectively afforded the corresponding products where the free amine undergoes Piancatelli rearrangement. Furthermore, acetyl‐monoprotected diamine and 4‐NO 2 ‐ or 4‐CF 3 ‐substituted aryldiamines/phenols afforded only traces of the corresponding products ( 332 , 335 and 338 , Scheme ) …”

“…Furthermore, acetyl-monoprotectedd iamine and 4-NO 2 -o r4 -CF 3 -substituted aryldiamines/phenols afforded only traces of the corresponding products (332, 335 and 338,S cheme 34). [44]…”

“…Reactionscope of the Lanthanum(III)-catalyzed formation of tri-cyclicCPs 323-338. [44] Scheme35. Donor-acceptor Stenhouse adducts (DASAs).…”

The Piancatelli Rearrangement: New Applications for an Intriguing Reaction

“…The isolated yields were high both with 2-aminothiophenols and 2-aminophenols, although 2-aminophenols required slightly longer reaction times, being less reactive. Curiously, nearly two months later, another group published [66] the same reaction sequence shown in Scheme 21 using La(OTf) 3 (5 mol %) as the catalyst and acetonitrile at reflux as the solvent. For the same substrates, yields were lower if compared with those obtained with In(OTf) 3 and reaction times were longer (Table 7).…”

Brønsted Acid Catalyzed Domino Aza‐Piancatelli Rearrangement/Michael Reaction: Construction of 1,4‐Benzodiazepin‐5‐ones in One Pot

“…A careful look at the products obtained by an aza‐Piancatelli reaction reveals that the cyclopentenone functionality can act as a Michael acceptor, which can be subject to the availability of an additional nucleophile on the aryl ring of the aniline moiety. [8a], We approximated that this secondary nucleophile would have to be less nucleophilic to avoid regiochemistry issues.…”