Benzothiazolyl- and benzimidazolyl-substituted 1-iminoisoindolines: synthesis, mechanistic studies, and crystal structure determination

Unusual reaction of (E)-2-[(benzo[d]thia-zol-2-yl-imino)-meth-yl]-5-(di-ethyl-amino)-phenol with tri-phenyl-borane: crystal structures and optical properties

The mol-ecular and crystal structure of (E)-2-[(benzo[d]thia-zol-2-yl-imino)-meth-yl]-5-(di-ethyl-amino)-phenol (C18H19N3O2S, Et2N-Bz) and its unexpected reaction product with tri-phenyl-borane, 2,2-diphenyl-1,3-dioxa-2-borata-1,2-di-hydro-naphthalene [systematic name: N,N-diethyl-2,2-diphenyl-2H-1,3λ3,2λ4-ben-zodioxaborinin-7-amine, C23H24BNO2, (I)] are described. For Et2N-Bz, the hydroxyl group is involved in an intra-molecular hydrogen bond with the imino nitro-gen atom and the C=N bond displays an E configuration. The crystal packing is characterized by layers of inversion dimers parallel to the (10) plane and chains of mol-ecule in the a-axis direction formed through C-H⋯O inter-actions. Complex (I) crystallizes with two mol-ecules (A and B) in the asymmetric unit, which differ in the orientation of the ethyl groups. The 1,3-dioxa-2-borata-1,2,3,4-tetra-hydro-naphthalene ring displays a slight envelope conformation with the boron atom as the flap. In the crystal packing, chains of alternating A and B mol-ecules formed by C-H⋯O hydrogen bonds run in the b-axis direction. The UV-vis absorption and emission properties of the compounds are discussed and their aggregation-induced emission properties are further investigated.

N-substitution Reactions of 2-Aminobenzimidazoles to Access Pharmacophores

Benzimidazole (BI) and its derivatives are interesting molecules in medicinal chemistry because several of these compounds have a diversity of biological activities and some of them are even used in clinical applications. In view of the importance of these compounds, synthetic chemists are still interested in finding new procedures for the synthesis of these classes of compounds. Astemizole (antihistaminic), Omeprazole (antiulcerative), and Rabendazole (fungicide) are important examples of compounds used in medicinal chemistry containing BI nuclei. It is interesting to observe that several of these compounds contain 2-aminobenzimidazole (2ABI) as the base nucleus. The structures of 2ABI derivatives are interesting because they have a planar delocalized structure with a cyclic guanidine group, which have three nitrogen atoms with free lone pairs and labile hydrogen atoms. The 10-π electron system of the aromatic BI ring conjugated with the nitrogen lone pair of the hexocyclic amino group, making these heterocycles to have an amphoteric character. Synthetic chemists have used 2ABI as a building block to produce BI derivatives as medicinally important molecules. In view of the importance of the BIs, and because no review was found in the literature about this topic, we reviewed and summarized the procedures related to the recent methodologies used in the N-substitution reactions of 2ABIs by using aliphatic and aromatic halogenides, dihalogenides, acid chlorides, alkylsulfonic chlorides, carboxylic acids, esters, ethyl chloroformates, anhydrides, SMe-isothioureas, alcohols, alkyl cyanates, thiocyanates, carbon disulfide and aldehydes or ketones to form Schiff bases. The use of diazotized 2ABI as intermediate to obtain 2-diazoBIs was included to produce Nsubstituted 2ABIs of pharmacological interest. Some commentaries about their biological activity were included.

Contemporary progress in the synthesis and reactions of 2-aminobenzothiazole: a review

Various protocols for the synthesis and reactions of 2-aminobenzothiazole.

Planarity of substituted pyrrole and furan rings in (3R*, 1′S*, 3′R*)-3-(1′-tert-butylamino-1′H, 3′ H-benzo[c]furan-3′-yl)-2-tert-butyl-2,3-dihydro-1H-benzo[c]pyrrol-1-one

The title structure, (3R*, 1′S*, 3′R*)-3-(1′-tert-butylamino-1′H,3′H-benzo[c]furan-3′-yl)-2-tert-butyl-2,3-dihydro-1H-benzo[c]pyrrol-1-one has been determined at 290 and 150 K by single-crystal X-ray diffraction. The structure comprises two symmetry independent molecules with very similar conformations which differ mostly by orientations of the tert-butyl groups, situated at the periphery of these molecules. The molecules are composed of two parts, the cores of which are isoindolinone and isobenzofuran rings being bound by C–C bonds. The planarities of the pyrrolone and furan rings are compared with the known structures retrieved from the Cambridge Crystal Structure Database. It transpires in the title molecules, the planarity of the carbonyl-substituted pyrrole rings is exceptionally distorted in contrast to the furan rings. This fact is just the opposite of the tendency inferred from the Cambridge Crystal Structure Database. The reason may be the influence of the voluminous tert-butyl group which is attached to the nitrogen of the pyrrole group, as well as short centroid–centroid distances between the carbonyl-substituted pyrrole and furan rings. Cohesion forces between the molecules and their parts are provided by weak interactions only: The packing suggests C–H···O, π–π-electron ring interactions, N–H···π-electron ring as well as C–H···π-electron ring interactions. The structure determination of the title compound, the product of the reaction of o-phthalaldehyde with tert-butylamine, has provided indication about the mechanism of a chemical reaction which resulted in the formation of the title molecule.