Industrial Distillation Aspects of Diketene.

Large-scale distillation is a challenge in many respects. Particularly difficult is the purification by distillation of a compound with limited thermal stability. This article describes various aspects of these difficulties with some possible solutions. Special emphasis is placed on the collaboration of different disciplines to find pragmatic solutions to these challenges. The purification of diketene in quantities of several 1000 ta-1 is an excellent example to illustrate the different requirements. Although the distillation of diketene has been carried out by several companies for many years, there are still some aspects that deserve special attention.

Cascade process for direct synthesis of indeno[1,2-b]furans and indeno[1,2-b]pyrroles from diketene and ninhydrin.

Novel and efficient multicomponent reactions (MCRs) involving diketene, ninhydrin (indane-1,2,3-trione) and one primary amine (3CR) or two different primary amines (4CR) were achieved for the successful synthesis of dihydro-4H-indeno[1,2-b]furan-3-carboxamides or tetrahydroindeno[1,2-b]pyrrole-3-carboxamides, respectively. The merits of this method are highlighted by using either commercially available or easily accessible starting materials, operational simplicity, facile workup procedure, efficient usage of all the reactants, tolerance of a variety of functional groups and ability to conduct under un-catalyzed reaction condition. The products were also isolated by just decantation of the solvent, and for the purification column chromatography was non-required.

Structural, thermochemical and kinetic insights on the pyrolysis of diketene to produce ketene.

Diketene (4-methylideneoxetan-2-one) is a precursor to the formation of either two molecules of ketene, or allene and CO2 using pyrolysis techniques. It is not known experimentally which of these pathways is followed, or indeed if both are, during the dissociation process. We use computational methods to show that the formation of ketene has a lower barrier than formation of allene and CO2 under standard conditions (by 12 kJ/mol). According to CCSD(T)/CBS, CBS-QB3 and M06-2X/cc-pVTZ calculations the formation of allene and CO2 is favoured thermodynamically under standard conditions of temperature and pressure; however, kinetically the formation of ketene is favoured from transition state theory calculations at standard and elevated temperatures.

Pyrazole-promoted synthesis of pyrrolo[3,4-c] quinoline-1,3-diones in a novel diketene-based reaction.

We describe the first classic example of green synthesis of pyrrolo[3,4-c]quinolones scaffolds by catalyst-free unusual reaction of diketene, isatin, and primary amines in ethanol in the presence of pyrazole as a promoter for 4 h. The whole structure of the new product was confirmed by X-ray analysis. The overall transformation involves the cleavage and generation of multiple carbon-nitrogen and carbon-carbon bonds. This report represents a simple and straightforward approach for the synthesis of pyrrolo[3,4-c]quinoline-1,3-diones, which has significant advantages like readily available precursors, non-use of toxic solvent, operational simplicity, mild conditions, good atom economy, and excellent yields; therefore it provides a green and sustainable strategy for access to a range of interesting N-containing heterocyclic compounds in medicinal and organic chemistry.