Three-Component GaHal₃-Promoted Reactions of Substituted Methylidenemalonates and Donor–Acceptor Cyclopropanes with Propargyl Halides: Cascade Diastereoselective Construction of Five-Membered Lactones

Abstract

A new cascade three-component process for high trans,trans-diastereoselective assembly of five-membered (1-halovinyl)lactones has been developed. The process is based on reactions of substituted methylidenemalonates and cyclopropanedicarboxylates with 3-haloprop-1-ynes in the presence of GaHal 3 and involves the intermediate in situ generation of 1,2-zwitterionic gallium complexes with [Ga-(L) 3 ] 3+ [GaX 4 − ] 3 composition. Chloro, bromo, and iodo derivatives can be obtained successfully. Mechanistic and stereochemical aspects of the process we developed have been studied and considered in detail.

Catalytic Cycloisomerization of Enyne Diesters Derived From 2‐Propargyloxyarylaldehydes

“…Transition metal halides promoted enyne diester cyclization is an important method for annulation providing access to carbo-and heterocycles. [1][2][3][4][5][6] The requisites of this type of cyclization are an electrophilic alkene (such as diethyl 2-arylidene malonate) bearing coordination site for metal halides and an alkyne which acts as the nucleophile. While the analogous ene-ene cyclization [7][8][9][10][11][12][13][14][15][16] is facile, enyne cyclization is less facile due to low nucleophilicity of alkyne and thus often requires highly electrophilic olefin containing three electron-withdrawing groups.…”

“…Transition metal halides promoted enyne diester cyclization is an important method for annulation providing access to carbo‐ and heterocycles [1–6] . The requisites of this type of cyclization are an electrophilic alkene (such as diethyl 2‐arylidene malonate) bearing coordination site for metal halides and an alkyne which acts as the nucleophile.…”

Synthesis of the Cationic Gallium Phthalocyanines and Their Catalytic Application in Gallium(III)-Activated Processes for Donor–Acceptor Substrates

“…In recent years, simple gallium compounds made it possible to significantly expand the range of organic reactions. They showed themselves especially well in the range of donor–acceptor cyclopropane − (DAC) reactions − and extend them to related substrates, in particular, styrylmalonates, and donor–acceptor alkenes (DAA) as an alternative to DAC.…”

“…It should be noted that gallium was found to be a unique element for this purpose. − At the moment, it has almost no alternatives for performing a wide range of efficient reactions . Why gallium?…”

“…Nearly all reactions of this family (with rare exceptions) require equimolar amounts of gallium halides (GaHal 3 ), usually 1–2 equiv, − which is an obvious drawback. In addition, if equimolar amounts of a mediator are used, it is extremely difficult to perform enantioselective reactions.…”