Tosylimidazole-mediated one-pot synthesis of 2-azetidinones

Abstract

Cyclocondensation of Schiff bases and substituted acetic acid with tosylimidazole afforded 2-azetidinones in good to excellent yields. This reaction works reliably well for monocyclic and spirocyclic 2-azetidinones. This reaction is green and efficient and the products can be purified by simple crystallisation.

Recent Advances in the Synthesis of Spiro‐β‐Lactams and Spiro‐δ‐Lactams

“…The use of diphosphorus tetraiodide as acid activator in the synthesis of two other xanthene‐9‐carboxylic acid derived C3 spiro‐β‐lactams, 34 c and 34 d , was also reported allowing the synthesis of the target molecules in good yields (71–75%) (Scheme 8b) [24] . The same type of spiro‐β‐lactams 34 e,f could also be prepared in good yields (70–72%) via cyclocondensation of xanthene‐9‐carboxylic acid ( 32 ) and aromatic imines in the presence of tosylimidazole ( 35 ) (Scheme 8c) [25] . Tosyl chloride was also used for xanthene‐9‐carboxylic acid ( 32 ) activation, with this approach leading to the synthesis of C3 spiro‐β‐lactams 34 g,i bearing a morpholine ring, in moderate to good yields (41–71%) (Scheme 8d) [26] …”

“…[24] The same type of spiro-β-lactams 34 e,f could also be prepared in good yields (70-72%) via cyclocondensation of xanthene-9-carboxylic acid (32) and aromatic imines in the presence of tosylimidazole (35) (Scheme 8c). [25] Tosyl chloride was also used for xanthene-9-carboxylic acid (32) activation, with this approach leading to the synthesis of C3 spiro-β-lactams 34 g,i bearing a morpholine ring, in moderate to good yields (41-71%) (Scheme 8d). [26] The same group reported the use of N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (37, EEDQ) as the carboxylic acid activator for the in situ generation of ketene 38 (Scheme 9).…”

An update on the synthesis and reactivity of spiro-fused β-lactams

“…36 To deal with these difficulties, the Zarei and Sardarian groups have independently devoted efforts to the preparation of a cyclic ketene from the corresponding xanthene-9-carboxylic acid 34 using different carboxylic activators 36 to synthesize spiro-β-lactams 37 by Staudinger reaction with imines 35 (Scheme 10, Table 1). 15,[36][37][38][39][40][41][42][43] The structure of 1-[3-(morpholin-4-yl)propyl]-4-(3-nitrophenyl)spiro[azetidine-3,9'-xanthen]-2-one -an analog of spiro-β-lactams 37 -was successfully determined for the first time by Akkurt via single-crystal X-ray analysis. 44…”

Practical and Scalable Synthesis of Isosorbide Derivatives Containing an Active Amine Group

“…After a series of experimental trials, reduction using a Staudinger reaction gave better results under milder reaction conditions and with a simple work-up. [16][17][18][19] Characterisation of products (6) and (9) In the 1 H NMR spectrum of the title compound 6, there were nine signals due to 13 hydrogen atoms. The peaks' type, number and shape are in accordance with compound 6.…”