Investigating Organization of Molecules that Facilitates Intermolecular Acyl Transfer in Crystals: Reactivity and X-ray Structures of O-Benzoyl-myo-inositol 1,3,5-Orthoesters

Crystal structure analysis of racemic 2,6‐di‐O‐benzoyl‐myo‐inositol 1,3,5‐orthobenzoate reveals helical organization of the molecules, remarkably similar to that observed earlier in crystals of racemic 2,6‐di‐O‐benzoyl‐myo‐inositol 1,3,5‐orthoformate. Both these dibenzoates are isostructural despite the bulkier phenyl substituent in place of hydrogen. Thelatter compound shows highly facile intermolecular benzoyl transfer reactivity in its crystals and as anticipated from the crystal structure, the orthobenzoate indeed exhibits facile benzoyl transfer reactivity in its crystals. 2‐O‐Benzoyl‐myo‐inositol 1,3,5‐orthoformate and the corresponding orthobenzoate also undergo transesterification in their crystals, but the specificity of acyl transfer is very low, and the reaction yields a mixture of products. The parameters of helical molecular assembly that facilitates acyl transfer in crystals have been investigated. A comparison of the molecular assemblies and lattice interactions in crystals of all the four compounds with the observed reactivity patterns show that facile acyl transfer reaction is brought about by a modular “reaction tunnel” formed by helical pre‐organization of molecules, favorable electrophile···nucleophile contacts and weak interactions that hold the acyl group in the “right” orientation for the attack by the nucleophile. Acyl transfer reaction in all the four derivatives was also carried out in solution for comparison.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)