Methyl tetra-O-acetyl-α-d-glucopyranuronate: crystal structure and influence on the crystallisation of the β anomer

Methyl tetra-O-acetyl-β-d-glucopyranuronate (1) and methyl tetra-O-acetyl-α-d-glucopyranuronate (3) were isolated as crystalline solids and their crystal structures were obtained. That of the β anomer (1) was the same as that reported by Root et al., while anomer (3) was found to crystallise in the orthorhombic space group P212121 with two independent molecules in the asymmetric unit. No other crystal forms were found for either compound upon recrystallisation from a range of solvents. The α anomer (3) was found to be an impurity in initially precipitated batches of β-anomer (1) in quantities <3%; however, it was possible to remove the α impurity either by recrystallisation or by efficient washing, i.e. the α anomer is not incorporated inside the β anomer crystals. The β anomer (1) was found to grow as prisms or needles elongated in the a crystallographic direction in the absence of the α impurity, while the presence of the α anomer (3) enhanced this elongation

Convenient and robust one-pot synthesis of symmetrical and unsymmetrical benzyl thioethers from benzyl halides using thiourea

A series of symmetrical and unsymmetrical benzyl thioethers have been synthesised using a one-pot reaction from benzyl halides and thiourea. This procedure avoids the isolation or handling of malodorous thiols and generates high yields of benzyl thioethers in excellent purity

Sulfoxides: potent co-crystal formers

The design of co-crystals requires knowledge of robust supramol. synthons. The sulfoxide is a potent H bond acceptor and was used as a co-crystal former with a range of NH functional groups, via N-H···O=S H bonds. The NH functional group retains favorable H bond motifs from its own structure in all cases where this is possible, with the sulfoxide interacting in a discrete, capping fashion in four cases and in a bifurcated, bridging fashion in the three other cases presented here. Crystallog. data are given for 7 co-formers, dibenzyl sulfoxide and cyclohexanecarbothioamide

Crystal polymorphs and transformations of 2-iodo-4-nitroaniline

Full crystal structural characterization of three crystal polymorphs of 2-iodo-4-nitroaniline was carried out: the triclinic, orthorhombic, and a new monoclinic form. Powder X-ray diffraction, differential scanning calorimetry, and infrared data on the three of these are reported. Solvent-mediated transformations were observed on the basis of changes in crystal morphology and data from an in situ laser probe. Transformation to the monoclinic form was observed in all cases. [Published as part of a virtual special issue of selected papers presented in celebration of the 40th Anniversary Conference of the British Association for Crystal Growth (BACG), which was held at Wills Hall, Bristol, UK, September 6-8, 2009

Synthesis of cyclic alpha-diazo-beta-keto sulfoxides in batch and continuous flow

Diazo transfer to beta–keto sulfoxides to form stable isolable alpha-diazo-beta-keto sulfoxides has been achieved for the first time. Both monocyclic and benzofused ketone derived beta-keto sulfoxides were successfully explored as substrates for diazo transfer. Use of continuous flow leads to isolation of the desired compounds in enhanced yields relative to standard batch conditions, with short reaction times, increased safety profile and potential to scale up

Crystal polymorphism of methyl 2,3,4-tri-O-acetyl-1-O-(trichloroacetimidoyl)-α-d-glucopyranouronate

The polymorphism of the glycoside donor methyl 2,3,4-tri-O-acetyl-1-O-(trichloroacetimidoyl)-α-d-glucopyranouronate (1) has been investigated. Two polymorphic forms (labelled Forms I and II) have been elucidated and fully characterised by DSC, PXRD and single crystal analysis, both crystallizing in the space group P21. Form I was obtained by crystallization from a wide range of solvents, while Form II was obtained only from ethyl acetate or isopropanol on certain occasions. Unit cell dimensions for Form I are a 14.0292(12), b 8.9641(8), c 16.8580(14) Å, β 94.285(2)°, and for Form II a 11.266(3), b 6.8889(17), c 13.921(4) Å, β 101.161(6)°. Z’ is 2 for Form I and 1 for Form II. Form I displays two moderate intermolecular hydrogen bonds in the unit cell whereas Form II shows no moderate hydrogen-bonding motifs. All three molecules in the two polymorphs differ significantly in their conformations, especially with respect to the methyl carboxylate and trichloroacetimidoyl group

Investigating the influence of the sulfur oxidation state on solid state conformation

Design, synthesis and structural characterization of a series of diphenylacetylene derivatives bearing organosulfur, amide and amine moieties has been achieved in which the molecular conformation is controlled through variation of the hydrogen bond properties on alteration of the oxidisation level of sulfur

Unzipping the dimer in primary amides by cocrystallization with sulfoxides

A systematic crystal engineering study was undertaken to investigate how different electronic substituents on the aromatic ring of primary aromatic amides impact on the ability of the amide to cocrystallize with dibenzyl sulfoxide. Amides which cocrystallize with dibenzyl sulfoxide form 1:1 cocrystals containing a discrete N-H•••O=S supramolecular synthon as well as the well-known C(4) amide chain. The combination of these two synthons give rise to linear chains of amide molecules, with each amide molecule capped by one sulfoxide molecule. Thus, the R 2(over)2 (8) dimer typically seen for primary amides is no longer present in these cocrystals. The influence of the amide due to electronic effects is similar to that observed for acids in cocrystals

Synthesis and reactivity of alpha-sulfenyl-beta-chloroenones, including oxidation and Stille cross-coupling to form chalcone derivatives

The synthesis of a range of novel α-sulfenyl-β-chloroenones from the corresponding α-sulfenylketones, via a NCS mediated chlorination cascade, is described. The scope of the reaction has been investigated and compounds bearing alkyl- and arylthio substituents have been synthesised. In most instances, the Z α-sulfenyl-β-chloroenones were formed as the major products, while variation of the substituent at the β-carbon position led to an alteration in stereoselectivity. Stille cross-coupling with the Z α-sulfenyl-β-chloroenones led to selective formation of Z sulfenyl chalcones, while the E α-sulfenyl-β-chloroenones did not react under the same conditions. Oxidation of the Z α-sulfenyl-β-chloroenones was followed by isomerisation, leading to the E α-sulfinyl-β-chloroenones. Stille cross-coupling with the E α-sulfinyl-β-chloroenones produced the E sulfinyl chalcones. Either the E or Z sulfinyl chalcones can be obtained by altering the sequence of oxidation and Stille cross-coupling