Recent Advances in Phosphine‐Promoted (4 + 1) Annulation Reactions

Abstract

Over the past two decades, the nucleophilic phosphine catalysis has effected many powerful annulation reactions and emerged as an intriguing platform for the generation of highly functionalized carbo‐ and heterocycles. In addition to the well‐established (3 + 2) annulation, the phosphine‐promoted (4 + 1) annulation has received increasing attention and developed rapidly in recent years, which complements the (3 + 2) annulation and also provides an alternative approach to structurally diverse five‐membered carbo‐ and heterocycles. This minireview summarizes the recent advances in phosphine‐promoted (4 + 1) annulation reactions according to the type of substrates used in the annulations.

Chemo- and Diastereoselective Synthesis of Pyrrolidines from Aroylformates and δ-Tosylamino Enones via P(NMe2)3-Mediated Reductive Amination/Base-Catalyzed Michael Addition Cascade

“…As a result, a plethora of synthetic methods have been established in the past few decades for efficient preparation of pyrrolidines . Among them, the (3 + 2) cycloaddition reactions, particularly the (3 + 2) cycloaddition of azomethine ylides with activated olefins and the (3 + 2) cycloaddition of donor–acceptor cyclopropanes with imines, are demonstrated to be powerful tools to prepare functionalized pyrrolidines. ,,, As an alternative to (3 + 2) cycloaddition, the (1 + 4) annulation of one carbon unit with nitrogen-containing four-atom conjugated systems provides a complementary access to five-membered N-heterocycles . Nevertheless, synthesis of pyrrolidines via (1 + 4) annulation is still underdeveloped, although it has manifested its effectiveness in preparation of pyrrolines .…”

Phosphorus-Based Catalysis

“…The broad substrate scope, mild reaction conditions, and diverse reaction modes have established nucleophilic phosphine catalysis as a powerful tool in organic synthesis. Since our group’s comprehensive review of phosphine organocatalysis in 2018, more than 80 new reports of nucleophilic phosphine catalysis have been published . A survey of the progress in nucleophilic phosphine catalysis for the past two years has revealed some interesting features.…”

Direct access to tetrasubstituted cyclopentenyl scaffolds through a diastereoselective isocyanide-based multicomponent reaction

“…Moreover, distinct formal (3+2) cycloadditions which have also been useful for the construction of enantioriched cyclopentenes derivatives employed N-heterocyclic carbene (NHC)-catalyzed reactions, [20][21][22] metal carbenoids, 23 and the ring opening of cyclopropanes. [24][25][26] Although less explored, formal (4+1) cycloaddition is also a suitable strategy and, according to the recent literature, [27][28][29] either phosphine 30 and metal-catalyzed 31 are versatile and powerful approaches for the construction of these five membered ring systems. In 2014, Fu and co-workers disclosed a biphenyl phosphine-catalyzed enantioselective (4+1) annulation of allenoates with Michael donors (Scheme 1b).…”

“…Although less explored, formal (4 + 1) cycloaddition is also a suitable strategy and, according to recent literature, 27–29 phosphine 30 and metal catalysis 31 are versatile and powerful approaches for the construction of these five membered ring systems. In 2014, Fu and co-workers disclosed a biphenyl phosphine-catalyzed enantioselective (4 + 1) annulation of allenoates with Michael donors ( Scheme 1b ).…”