Reactions of <i>o</i>‑Quinone Methides with Pyridinium Methylides: A Diastereoselective Synthesis of 1,2-Dihydronaphtho[2,1‑<i>b</i>]furans and 2,3-Dihydrobenzofurans

A simple, general route to the 1,2-dihydronaphtho­[2,1-<i>b</i>]­furans and 2,3-dihydrobenzofurans substituted at C-2 by an acyl or aryl group, starting from phenolic Mannich bases and pyridinium ylides, has been developed. The mechanism of the reaction is believed to involve the formation of the <i>o</i>-quinone methide intermediate, Michael-type addition of the ylide to the <i>o</i>-quinone methide, followed by intramolecular nucleophilic substitution

Reaction of Push–Pull Enaminoketones and <i>in Situ</i> Generated <i>ortho</i>-Quinone Methides: Synthesis of 3‑Acyl‑4<i>H</i>‑chromenes and 2‑Acyl‑1<i>H</i>‑benzo[<i>f</i>]chromenes as Precursors for Hydroxybenzylated Heterocycles

A simple and efficient method for the synthesis of 4<i>H</i>-chromenes and 1<i>H</i>-benzo­[<i>f</i>]­chromenes containing a trifluoroacetyl or aroyl group in the pyran ring from <i>o</i>-quinone methide precursors and push–pull enaminoketones has been developed. The chromenes are presumably formed through an initial oxa-Diels–Alder reaction, followed by an elimination of amine. The possibility of further transformations of given chromenes to <i>o</i>-hydroxybenzylated pyrazoles, isoxazoles, and pyridines has been demonstrated

An Inverse Electron Demand Azo-Diels–Alder Reaction of <i>o</i>‑Quinone Methides and Imino Ethers: Synthesis of Benzocondensed 1,3-Oxazines

We have studied the reactions of <i>o</i>-quinone methide precursors with imino ethers. The reaction provides a versatile route to substituted 1,3-benzoxazines. The proposed reaction mechanism involves the generation of the <i>o</i>-quinone methide intermediates, imino-Diels–Alder reaction, and elimination. This cascade process is a rare example of the participation of imino ethers as dienophiles