title: Intramolecular Cyclization of Carbonate and Thiocarbonate Derivatives of myo-Inositol in the Solid State: Implications for Acyl Group Transfer Reactions in Molecular Crystals.
abstract: Racemic 4-O-phenoxycarbonyl and 4-O-phenoxythiocarbonyl derivatives of myo-inositol orthoformate undergo thermal intramolecular cyclization in the solid state to yield the corresponding 4,6-bridged carbonates and thiocarbonates, respectively. The thermal cyclization also occurs in the solution and molten states, but less efficiently, suggesting that these cyclization reactions are aided by molecular pre-organization, although not strictly topochemically controlled. Crystal structures of two carbonates and a thiocarbonate clearly revealed that the relative orientation of the electrophile and the nucleophile in the crystal lattice facilitates the intramolecular cyclization reaction and forbids the intermolecular reaction. The correlation observed between the chemical reactivity and the non-covalent interactions in the crystal of the reactants provides a way to estimate the chemical stability of analogous molecules in the solid state.
authors.affiliation: Division of Organic Chemistry, CSIR-National Chemical Laboratory, Pune, 411 008 (India).
authors.forename: Majid I
authors.initials: MI
authors.lastname: Tamboli
authors.affiliation: Division of Organic Chemistry, CSIR-National Chemical Laboratory, Pune, 411 008 (India). ms.shashidhar@ncl.res.in.
authors.forename: Mysore S
authors.initials: MS
authors.lastname: Shashidhar
authors.affiliation: Center for Materials Characterization, CSIR-National Chemical Laboratory, Pune, 411 008 (India). rg.gonnade@ncl.res.in.
authors.forename: Rajesh G
authors.initials: RG
authors.lastname: Gonnade
authors.affiliation: Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036 (India).
authors.forename: Shobhana
authors.initials: S
authors.lastname: Krishnaswamy
keywords: crystal engineering; cyclitols; inositols; nucleophilic substitution; solid-phase synthesis