Synthesis of substituted imid(thi)azolidines by [3+2] cycloaddition of aziridines with nitriles(isothiocyanates) via visible light photocatalysis

Abstract

The [3+2] cycloaddition reaction of aziridines with nitriles (isothiocyanates) has been developed using visible light photocatalysis. Two types of five-membered heterocyclic compounds, imidazolidines and thiazolidines, were synthesized in mild conditions. An oxidative quenching cycle mechanism is probably involved.

Expedient Synthesis of 2‐Iminothiazolidines via Telescoping Reactions Including Iron‐Catalyzed Nitrene Transfer and Domino Ring‐Opening Cyclization (DROC)

“…70 %) and is thus a good compromise (Table 3). The conversion is not complete because of the formation of several by‐products in little amount, which are probably coming from rearrangements when aziridine is opened [42] …”

“…The conversion is not complete because of the formation of several by-products in little amount, which are probably coming from rearrangements when aziridine is opened. [42] In order to investigate the substrate scope of the reaction and get insights into its mechanism, we have varied the para-substituent of styrene (R) and the substituent of the isothiocyanate (R').…”

Visible-Light-Promoted Click [3+2] Cycloaddition of Aziridine with Alkyne: An Efficient Synthesis of Dihydropyrrolidine

“…Based on literature precedents 14 15a 16 and our observations (Table 1 , entries 2 and 3), a plausible reaction mechanism is proposed to illustrate the oxidative [3+2]-cycloaddition reaction (Scheme 2 ). Initially under visible-light irradiation, the ground state of Ru 2+ is changed to excited state (Ru* 2+ ) which is oxidized by PhN 2 BF 4 ( 4 ) to produce Ru 3+ .…”

“…On using (NH 4 ) 2 S 2 O 8 as the oxidant, the product was obtained in 61% yield (entry 10). 16 When the concentration of PhN 2 BF 4 was changed to 5 mol%, 10 mol%, 20 mol%, and 50 mol%, the product was obtained in 10%, 16%, 33%, and 72% yield, respectively (entry 11). A small amount of biphenyl was also detected in the reaction mixture.…”

Arylethanolamines in Ritter reaction: Synthesis of 2,4‐Diarylimidazole Core

“…[21] Nevertheless, the most widely studied direction is a ring-expansion of 2-arylaziridines with nitriles promoted by photocatalyst, Brønsted-Lowry or Lewis acids (Figure 1d). [22][23][24][25][26][27][28] Considering the latter approach, we came to the conclusion that like arylaziridines, arylethanolamines could provide a synthetic equivalent for the key synthon of this process -dipole A. Ethanolamines 3 are a widespread skeleton of alkaloids and pharmaceuticals, [29,30] and are readily available in two steps from aromatic aldehydes 1, sarcosine and paraformaldehyde via azomethine ylide's cycloaddition and subsequent demethylenation of 5-aryloxazolidines 2 (Scheme 1). [31] Arylethanolamines 3 represent benzylic alcohols and therefore could react with nitriles in Ritter reaction [32] with the subsequent intramolecular cyclization of the secondary amine at amide group leading to the desired imidazolines.…”