A novel reaction of 2-phenacyl mercaptoimidazole with acetic anhydride: formation of an imidazothiazole with loss of a p
- PDF / 708,158 Bytes
- 8 Pages / 595.276 x 790.866 pts Page_size
- 2 Downloads / 135 Views
Indian Academy of Sciences Sadhana (0123456789().,-volV)FT3](0123456 789().,-volV)
REGULAR ARTICLE
A novel reaction of 2-phenacyl mercaptoimidazole with acetic anhydride: formation of an imidazothiazole with loss of a phenyl group SHASHIPRABHAa,*, K NAGARAJANa,d,*, SAJESH P THOMASb, SURESH P NAYAKc, K SUNDARRAJA RAOa, K SHRIDHARAa and T N GURU ROWb a Alkem Laboratories Ltd., b Solid State and Structural
R&D Centre, Bangalore 560 058, Karnataka, India Chemistry Unit, Indian Institute of Science, Bangalore 560 012, Karnataka, India c Department of Chemistry, Mangalore University, Mangalore, Karnataka, India d Present address: #1, 1st Floor, House No. 007. Serene Urbana, Ozone Urbana, Southegowdanahalli, Bangalore 562 110, India E-mail: [email protected]; [email protected] MS received 15 April 2020; revised 23 June 2020; accepted 4 July 2020
Abstract. Attempted cyclodehydration of phenacyl mercaptoimidazole hydrobromide with acetic anhydride gave an abnormal product lacking the phenyl group. The molecular structure is confirmed using X-ray crystal structure studies. Phenacyl mercaptobenzimidazole hydrobromide behaved similarly. Analysis of crystal structure revealed an intermolecular S…Br chalcogen bonding interaction. Keywords. Phenacyl mercaptoimidazole; acetic anhydride; imidazo[2,1-b] thiazole; Single crystal.
1. Introduction The imidazothiaoles and their precursors, thioacetophenones are frequently being used as a structural unit in the tailoring of pharmaceutical compounds with a wide range of activities.1 Approaches for the synthesis imidazothiazoles via heteroaryl thioacetophenones are represented by many examples.2–4 Mazur et. al.,5 reported that the reaction of 2-mercaptoimidazole and its 4(5)-aryl-and 4,5-diaryl substituted derivatives with a-halogenoketones gives a number of alkyl-, acyl-, and aryl-substituted
imidazo[2,1-b]thiazoles. They also reported that when 2-mercaptoimidazole (1) was boiled with aliphatic ahalogenoketones in ethanol or butanol in the absence of alkali, imidazo[2,1-b]thiazoles (3) are formed whereas the reaction of 2-mercaptoimidazole with aromatic halogenketones under similar condition stops at the stage of 2-imdazolylthioacetophenones (2). In the same literature, it was also reported that 2-imidazolylthioacetophenones cyclize to form aryl-substitutedimidazo[2,1b]thiazoles only under the action of strong water abstracting reagents such as phosphorus oxychloride. 2
R R
Hal
H N
3
SH
N
4 3
COR
1
2
R CHCOR
R R
4
1 (R , R =H)
3
4
H N N
CHR S
2
R
1
-H2O
R
R
3
R
N
4
2 1
S
N 3
R1=H, Ac: R2 =Alk, Ar: R3=H, Ar: R4=H, Ar *For correspondence Electronic supplementary material: The online version of this article (https://doi.org/10.1007/s12039-020-01824-y) contains supplementary material, which is available to authorized users.
120
Page 2 of 8
1
J. Chem. Sci. (2020)132:120
2
3
4
R = H, Ac: R = Alk, Ar: R = H, Ar: R = H, Ar Abd EI-Wareth A. O. Sarhan et. al.,6 reported the reaction of 2-mercaptobenzimidazole (4) with achloroaromatic ketones g
Data Loading...
