Hydrogen bonding networks in chiral thiourea organocatalysts. Evidence on the importance of the aminoindanol moiety. Gimeno, M. C.; Herrera, R. P. Cryst. Growth Des., 2016, 16, 5091–5099.
Abstract. The crystal structures of four chiral thioureas, which are normally used as organocatalysts, are reported by the first time.
Each compound is assembled in the crystal in a different way according to their chiral moiety in the thiourea skeleton, being dependent
on the presence or the absence of the OH group in the aminoindanol or aminoindane moiety, respectively. Thiourea 1, which contains an aminoindane group, is assembled into a zigzag chain linked via N-H•••S hydrogen bonds. Thiourea 2, with an aminoindanol and a phenyl group, interacts mainly through O-H•••S and N-H•••S bonds in a very congested structure. Thiourea 3 disposes in a zigzag chain mainly through S•••OH bonds and in further superposed zigzag chains through NH•••S hydrogen bonds. The compound 4 is coordinated in a coplanar organization via O•••H-N interactions, forming very tight dimers, which are further arranged in chain of dimers through O-H•••S interactions. The general trends in the patterns of packing of these four compounds are compared to those commonly observed in the crystalline solids of other thiourea and urea structures. The different arrangements adopted by our chiral thioureas in the solid state are rationalized and discussed in terms of molecular structure, remarking the importance of the OH group in the aminoindanol scaffold in the determination of the preferred solid assembly. A comparison correlating the crystal structures, specifically the interactions in the crystal network and the configuration adopted by the thioureas, with the catalytic efficiency previously observed by the same structures, is included.