Six‐Membered Ring Formation from Lewis Acid Promoted Reactions of 2‐Substituted 2‐Alkenyl Amides and Esters of Ethenetricarboxylate

Abstract

The Lewis acid promoted reactions of 2‐substituted 2‐propenyl amides and the 2‐methylbuta‐2,3‐dienyl ester of ethenetricarboxylate have been examined. The reactions of 2‐substituted 2‐propenyl amides with AlCl3 gave 2‐oxo‐5,6‐dehydropiperidines as the major products. The reaction of 2‐methylbuta‐2,3‐dienyl ester with Lewis acids such as AlCl3 and SnCl4 gave 2‐oxo‐3,6‐dihydropyran as the major product. The preference for six‐ over five‐membered‐ring formation was observed.

Lewis Acid Catalyzed Cyclization Reactions of Ethenetricarboxylates via Intramolecular Hydride Transfer

“…This product 11 may be formed via intermolecular hydride transfer, although the detailed mechanism is not clear yet. The difference on reactivity between oxygen and nitrogen analogues can be explained, similar to the cyclization of other ethenetricarboxylate derivatives . Triester 10 may be more stable in the s- cis conformation, probably because of the steric repulsion.…”

“…We have developed various ring formation reactions utilizing ethene­tricarboxylates as highly electrophilic CC components . In order to develop general synthetic methodology for the construction of the heterocycles, we have investigated the use of more reactive electrophilic substrates than alkylidene and arylidene­malonates, ethene­tricarboxylates.…”

Sc(OTf)3-Catalyzed Cyclization of Allyl Amides of Ethenetricarboxylate

“…Reaction of allyl amides of ethenetricarboxylate {2-[(Nallylcarbamoyl)methylene]malonates} 1a-c with catalytic amounts of various Lewis acids was examined to test whether any cycloisomerized products could be observed. 11 The reaction of 1a with AlCl 3 (0.2 equiv) gave chlorinated 2oxopyrrolidine 3a (the structure is shown in Table 1) in 35% yield. 10a The reaction of 1a with Zn(OTf) 2 did not proceed at 80 °C and the use of In(OTf) 3 gave a complex mixture.…”

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.…”