Asymmetric 1,3-dipolar cycloadditions of acrylamides

Abstract

This critical review, which is relevant to researchers in synthetic organic chemistry, focuses on asymmetric 1,3-dipolar cycloadditions with acrylamides. The use of chiral acrylamides as dipolarophiles leads to high levels of stereocontrol, due to conformational constraint in the acrylamides. Employment of chiral tertiary acrylamides containing nitrogen heterocycles is particularly effective in controlling the stereoselectivity. Following a general overview of 1,3-dipolar cycloadditions, the main body of the review focuses on asymmetric 1,3-dipolar cycloadditions of acrylamides with nitrile oxides, nitrones, diazoalkanes and azomethine ylides, with particular emphasis on the rationale for the observed stereocontrol (215 references)

1,3-Dipolar cycloadditions of 2-thio-3-chloroacrylamides with diazoalkanes

“…All spectra were recorded at room temperature (~20 °C) in deuterated chloroform (CDCl 3 ) unless otherwise stated using tetramethylsilane (TMS) as an internal standard. 1 H NMR spectra that were recorded in deuterated dimethylsulfoxide (DMSO-d 6 ) were assigned using the DMSO peak as the Diazomethane was generated from Diazald ® in glassware containing clear glass joints. 45 Diazoethane was generated from N-ethyl-N-nitrosourea 46,47 and phenyldiazomethane from the vacuum pyrolysis of benzaldehyde tosylhydrazone.…”

“…1 The versatility of the cycloaddition is evident in the structural variety of the 4 and 2 components, including functionality such as C≡C, C=C, C≡N, C=N, C=O, and C=S with both isolated or conjugated systems.…”

Asymmetric 1,3-Dipolar Cycloadditons of Stabilized Azomethine Ylides with Nitroalkenes

“…Such as it was mentioned before, since 2002 many contributions employing chiral Lewis acids or chiral organocatalysts have been compiled in the literature [13][14][15][16][17][18][19][20]. The number of catalysts and their efficiency contribute to the preparation of multiple and sophisticated molecules with well defined absolute configuration.…”

“…These applications and properties of the mentioned compounds represent a small part of the enormous interest of prolines and pyrrolidines in many scientific areas [10][11][12]. All this series of compounds C, bearing attached a nitro group, can be prepared in a straightforward manner employing asymmetric 1,3-dipolar cycloadditions (1, between stabilized azomethine ylides generated from imino esters A or even its corresponding iminium salt A' and nitroalkenes B [13][14][15][16][17][18][19][20] employing very mild reaction conditions according to the retrosynthetic pathway shown in (Scheme 1). The most employed 1,3-dipole in the literature is the azomethine ylide [21][22][23][24][25][26][27], which can be generated from diverse routes [22].…”

Synthesis and stereoselective oxidation of α-thio-β-chloropropenyloxazolidin-2-ones

“…While amides have been employed as chiral auxiliaries in asymmetric synthesis with some success, 4 use of oxazolidinones as chiral auxiliaries has in many instances led to excellent relay of stereochemistry. [5][6][7][8][9][10] Chiral 2-oxazolidinones, first reported by Evans in 1981, 5 have proven to be highly versatile chiral auxiliaries, with high asymmetric induction achieved in alkylations, aminations, azidations, brominations, hydroxylations, aldol additions, DielsAlder cycloadditions and conjugate reactions.…”