Vinylogous and Arylogous Stereoselective Base-Promoted Phase-Transfer Catalysis

Abstract

Vinylogous enolate and enolate-type carbanions, generated by deprotonation of α,β-unsaturated compounds and characterized by delocalization of the negative charge over two or more carbon atoms, are extensively used in organic synthesis, enabling functionalization and C–C bond formation at remote positions. Similarly, reactions with electrophiles at benzylic and heterobenzylic position are performed through generation of arylogous and heteroarylogous enolate-type nucleophiles. Although widely exploited in metal-catalysis and organocatalysis, it is only in recent years that the vinylogy and arylogy principles have been translated fruitfully in phase-transfer catalyzed processes. This review provides an overview of the methods developed to date, involving vinylogous and (hetero)arylogous carbon nucleophiles under phase-transfer catalytic conditions, highlighting main mechanistic aspects.

An Access to Chiral Phthalides: Enantioselective Synthesis of Escitalopram

“…Thanks to this, phasetransfer catalysis proved to be suitable for many arylogous CÀ C bond formation where homogeneous organocatalysis has failed. [10] In this respect, we recently reported the highly diastereoselective arylogous Michael addition of γ-aryl phthalides catalyzed by alkali bases and crown ethers. [8] The extension of this methodology to γ-unsubstituted phthalides was achieved by adding stoichiometric amounts of the silylating agent N,O-bis(trimethylsilyl)acetamide (BSA).…”

“…This latter feature allows the activation of extremely weakly acidic pronucleophiles, despite the non‐anhydrous conditions employed. Thanks to this, phase‐transfer catalysis proved to be suitable for many arylogous C−C bond formation where homogeneous organocatalysis has failed [10] . In this respect, we recently reported the highly diastereoselective arylogous Michael addition of γ‐aryl phthalides catalyzed by alkali bases and crown ethers [8] .…”

Flexible and Convergent Enantioselective Total Synthesis of (R)-Juglanaloids A and B: Two Phthalide Spiro Alkaloids with Potential Alzheimer’s Disease Inhibitory Activity

“…In the variegated panorama of natural products, the chiral phthalide framework is a recurrent structural motif that is frequently associated with relevant and diverse biological activities and therefore object of continuous effort in developing stereoselective synthetic methodologies. , On our side, given the large availability of simple phthalide building blocks, we have pursued over the past few years a strategy for building more complex structures based on the stereocontrolled formation of a C–C bond at the γ-site of the lactone ring. , …”

Advances in organocatalyzed synthesis of organic compounds

“…[45][46][47][48][49][50] Functionalized anthrone derivatives can be synthesised by non-asymmetric and asymmetric 1,4-addition, as well as Diels-Alder reactions. [51][52][53][54] While Kitamura et al reported the coupling of 2-hydroxyindoline with anthrone using BF 3 -$Et 2 O, 55 and White's group established a two-step technique employing Fe(PDP)-catalyzed oxidation followed by 1,2-addition of anthrone, 56 the 1,2-addition of imine remains undiscovered. Recently, researchers reported for the rst time a Et 3 N direct 1,2-addition of anthrone to N-sulfonylaldimines over moderate conditions, resulting in benzyl amine functionalized anthrone.…”