Reactions of Acid Chlorides/Ketenes with 2‐Substituted 4,5‐Dihydro‐4,4‐dimethyl‐1,3‐thiazoles: Formation of Penam Derivatives

Abstract

Addition reactions of acid chlorides with various 2-substituted 4,5-dihydro-4,4-dimethyl-5-(methylsulfanyl)-1,3-thiazoles under basic conditions were studied. Two kinds of products were obtained from these additions, beta-lactams and non-beta-lactam adducts. When the reaction was carried out with 4,5-dihydro-1,3-thiazoles with a Ph substituent at C(2), the reaction proceeded via formal [2+2] cycloaddition and led to the correspoding beta-lactam. On the other hand, acid chlorides and 4,5-dihydro-1,3-thiazoles bearing an alpha-H-atom at the C(2)-substituent underwent C(alpha)-and/or N-addition reactions and furnished non-beta-lactam adducts, i.e., C(alpha)-and/or N-acylated 1,3-thiazolidines. The attempted transformations of sulfonyl esters of exo-6-hydroxy penams to endo-6-azido penams failed, although they were successful with mono-beta-lactams under the same conditions.

Acyclic Twisted Amides

“…In general, the amide bond geometry of structurally characterized β-lactams presented in Figures and − can be characterized as N-pyramidalized (average χ N of 54.4°), while twist is less significant (average τ of 19.2°), as expected from the geometry of the fused four-membered ring system. There is only a very scattered correlation between N-pyramidalization and twist of the amide bond, with the general trend of higher twist with increased nitrogen pyramidalization ( R 2 = 0.30).…”

“…The most common are [ 2 .4.0] and [ 2 .3.0] ring systems with the six-membered ring such as 1,3-oxazinane (e.g., 4.30 ), and more common five-membered ring, such as thiazolidine 1,1-dioxide (e.g., 4.32 ), thiazolidine 1-oxide (e.g., 4.33 ), thiazolidine (e.g., 4.34 ), 1,3-selenazolidine (e.g., 4.36 ), pyrrolidine (e.g., 4.81 ), imidazolidine (e.g., 4.94 ), or oxazolidine (e.g., 4.101 ) . In general, more dense substitution of the fused ring, in particular at the α-positions to the nitrogen atom and the carbonyl group and ring unsaturation, result in higher N-pyramidalization. − These N-pyramidalized amides are well-known to be highly reactive as acylating reagents and are important pharmacophores in medicinal chemistry research.…”

Design, Synthesis, and Evaluation of the Anticancer Properties of Novel Quinone Bearing Carbamyl β‐Lactam Hybrids

“…The 1 H nuclear magnetic resonance (NMR) spectra of crude compound ( 3 ) showed the presence of imine C─H proton at 8.89 ppm as singlet with 92% GC–MS purity. Our study was initiated with the optimization of Staudinger reaction based on reported literature . In an initial experiment, treatment of imine ( 3 ) with acetoxyacetyl chloride ( 4 ) under general condition using Et 3 N and CH 2 Cl 2 as solvent at room temperature provided complex mixture.…”