Synthesis and structural characterization of 1-arylimidazole-2-thiones and N,N′-aryldiethoxyethylthioureas with electronically diverse substituents: a manifold of hydrogen bonding networks

Abstract

The 1-arylimidazole-2-thiones, (HmimAr) [Ar = 3,4,5-C6H2(OMe)3, 2,4-C6H3(NO2)(OMe), 2,4,6-C6H2Cl3 and 3,5-C6H3(CF3)2], which feature electronically diverse substituents, may be obtained via acid-catalyzed ring closure of the corresponding N,N′-aryldiethoxyethylthiourea derivatives, ArN(H)C(S)N(H)CH2CH(OEt)2, (H2detuAr), which in turn are obtained via treatment of aminoacetaldehyde diethyl acetal, H2NCH2CH(OEt)2, with the respective arylisothiocyanates (ArNCS). The molecular structures of all of the above N,N′-aryldiethoxyethylthioureas and 1-arylimidazole-2-thiones have been determined by X-ray diffraction, thereby demonstrating that the substituents have a profound effect on the crystal structures. For example, each of the N,N′-aryldiethoxyethylthiourea derivatives adopts a different hydrogen bonding pattern. Specifically, the hydrogen-bonding network in (i) H2detuArCl3 consists of chains of 9-membered rings, with an [ R22(9)] motif, that feature one N–H ⋯ O and one N–H ⋯ S interaction, (ii) H2detuArOMe,NO2 consists of chains of 6-membered rings, with an [ R21(6)] motif, that feature two head-to-tail N–H ⋯ S interactions, (iii) H2detuAr(CF3)2 consists of a dimer that features two pairs of N–H ⋯ O interactions, of which each pair is a component of an 8-membered ring with an [ R22(8)] motif, and (iv) H2detuAr(OMe)3 consists of a chain of head-to-head dimeric rings with a basic [ R22(16)] motif, a notable feature of which is that sulfur does not play a role as a hydrogen bond acceptor. Each of the 1-arylimidazole-2-thiones exists as a “head-to-head” hydrogen-bonded dimer in the solid state, with an [ R22(8)] motif. However, while the hydrogen-bonded motifs for HmimArCl3 and HmimAr(OMe)3 are planar, those for HmimAr(CF3)2 and HmimArOMe,NO2 are extremely puckered, with fold angles of 24.2° (mean value) and 45.7°, respectively.

Metal‐Free Transfer C−H Borylation of Substituted Thiophenes

“…The procedure yielded 767 mg (49 %) of the title compound as a pale‐yellow solid. Spectral data is consistent with the literature [48] . 1 H NMR (400 MHz, CDCl 3 ) δ 12.04 (s, 1H), 8.20 (s, 2H), 7.94 (s, 1H), 6.97 (d, J =2.5 Hz, 1H), 6.91 (d, J =2.5 Hz, 1H).…”

Protolytic Cleavage of Hg–C Bonds Induced by 1-Methyl-1,3-dihydro-2H-benzimidazole-2-selone: Synthesis and Structural Characterization of Mercury Complexes

“…1-R-imidazole-2-thiones, H(mim R ), 20 − 22 of which the methyl derivative is the well-known antithyroid drug, methimazole (tapazole), 23 , 24 are a widely studied class of molecules that can bind to a variety of metals, 25 − 27 including mercury. 27 However, in contrast to the numerous studies pertaining to 1-R-imidazole-2-thiones, there are few corresponding investigations of 1-R-imidazole-2-selones, H(seim R ).…”

“…1-R-imidazole-2-thiones, H­(mim R ), − of which the methyl derivative is the well-known antithyroid drug, methimazole (tapazole), , are a widely studied class of molecules that can bind to a variety of metals, − including mercury . However, in contrast to the numerous studies pertaining to 1-R-imidazole-2-thiones, there are few corresponding investigations of 1-R-imidazole-2-selones, H­(seim R ). − For example, only H­(seim Me ) , and H­(seim Mes ), and the benzannulated derivatives, H­(sebenz­im Me ) , and H­(se­benzim Bu t ), have been synthesized and structurally characterized (Figure ).…”