Organocatalytic Asymmetric Domino Oxa-Michael–Mannich-[1,3]-Amino Rearrangement Reaction of N-Tosylsalicylimines to α,β-Unsaturated Aldehydes by Diarylprolinol Silyl Ethers

Abstract

An organocatalytic asymmetric enantioselective domino oxa-Michael–Mannich-[1,3]-amino rearrangement reaction of N-tosylsalicylimines with a wide range of α,β-unsaturated aldehydes utilizing diarylprolinol silyl ether catalysis is described. The catalytic reactions proceed with excellent enantioselectivity (up to 99% ee) to produce the corresponding chair N-tosylimines-chromenes with a yield of up to 99%, tolerating a range of functional groups. This methodology offers a new method with great potential to further extend the synthetic power and versatility of chiral aminocatalysis.

Piperidine-Iodine as Efficient Dual Catalyst for the One-Pot, Three-Component Synthesis of Coumarin-3-Carboxamides

“…Thirdly, an intramolecular cyclization produces intermediate chroman-2-one II , which suffers a second intramolecular cyclization to afford intermediate beta-lactam III . Finally, a [ 1 , 3 ]-amino rearrangement involving the β-lactam results in the formation of the target molecule 3a [ 38 ]. During the reaction mechanism, iodine is proposed to activate the imine and carbonyl groups as it behaves as a mild Lewis acid [ 39 ], thus facilitating the transformations, as long as piperidine acts as a base, which allows for protonic transferences [ 32 ].…”

Enantioselective Organocatalytic Michael Addition Reactions Catalyzed by Proline/Prolinol/Supported Proline based Organocatalysts: An Overview

“…Recently, Sha Hu et al [91] . developed an enantioselective domino oxa‐Michael‐Mannich‐ [1,3]‐amino rearrangement sequence for the very first time involving N‐tosylsalicylimines 243 with α,β ‐unsaturated aldehydes 244 catalyzed by X in presence of para ‐nitro benzoic acid and toluene at 0 °C, yielding a broad range of chair N‐tosylimines‐chromenes 245 in high yields (up to 99 %) with excellent enantioselectivity (up to 99 % ee).…”

“…It is supposed that an intermediate 246 , a four‐membered nitrogen‐containing ring undergoes [1,3]‐amino rearrangement, leading to the generation of the desired product 245 [Scheme 61]. [91] …”