Multiphase oxidation of alcohols and sulfides with hydrogen peroxide catalyzedby heteropolyacids

This work describes the application of a multiphase system for the oxidation of alcohols to ketones or aldehydes, and the selective conversion of sulfides to sulfoxides or sulfones using Keggin-type heteropolyacids and hydrogen peroxide. Benzylic and secondary alcohols were oxidized to ketones or aldehydes at 70 °C in good yield and selectivity. Similarly, sulfides were converted to sulfoxides or sulfones at room temperature with high yields and selectivity

Reaction of dialkyl carbonates with alcohols:Defining a scale of the best leaving and entering groups

A series of dialkyl and methyl alkyl carbonates has been synthesized and their reactivity investigated. The behavior of preferential leaving and entering groups for the newly synthesized carbonates has been accurately investigated. Both experimental and computational studies agreed that the scale of leaving groups follows the trend: PhCH2O–, MeO– ≥ EtO–, CH3(CH2)2O–, CH3(CH2)7O– > (CH3)2CHO– > (CH3)3CO–. Accordingly, the scale of the entering group has the same trend, with t-butoxide being the worst entering group. A preliminary attempt to rationalize the nucleofugality trends, limited to the (CH3)3CO– and CH3O– groups, has indicated that a likely origin of the observed trends lies in the different entropic contributions and solvation effects

Chemical Behavior and Reaction Kinetics of Sulfur and Nitrogen Half-Mustard and Iprit Carbonate Analogues

Sulfur and nitrogen mustards are very toxic, yet versatile organic molecules with numerous applications. Herein, we report on a synthesis of a new class of green compounds, i.e., half-mustard and iprit carbonates, that result in new, unexplored, and safe molecules. Their chemical behavior with several nucleophiles and their reaction kinetics have been investigated

A Comparative Environmental Assessment for the Synthesis of 1,3-Oxazin-2-one by Metrics: Greenness Evaluation and Blind Spots

Alternative syntheses for the production of 3-benzyl-1,3-oxazinan-2-one are compared and evaluated employing green metrics. An environmental assessment has been performed using the algorithm recently developed by Andraos that takes into account the mass flows and the software EATOS that considers mass flows, environmental impacts of the substances involved, and waste produced. Strengths and critical spots of the environmental tools employed are also discussed. Data collected showed that the synthesis employing diethyl carbonate is the most promising one, having the lowest environmental impact

Highly Selective Phosgene-Free Carbamoylation of Aniline by Dimethyl Carbonate under Continuous-Flow Conditions

Over the last 20 years organic carbamates have found numerous applications in pesticides, fungicides, herbicides, dyes, pharmaceuticals, cosmetics, and as protecting groups and intermediates for polyurethane synthesis. Recently, in order to avoid phosgene-based synthesis of carbamates, many environmentally benign and alternative pathways have been investigated. However, few examples of carbamoylation of aniline in continuous-flow apparatus have been reported. In this work, we report a high-yielding, dimethyl carbonate (DMC)-mediated carbamoylation of aniline in a fixed-bed continuously fed reactor employing basic zinc carbonate as catalyst. Several variables of the system have been investigated (i.e. molar ratio of reagents , flow rate, and reaction temperature) to optimize the operating conditions of the system

Dimethyl Carbonate: An Innovative and Eco-Sustainable Solvent and Reagent

Green Chemistry is a recent phenomenon. Even if environmental statutes and regulations have already proliferated since the early 1960s a combination of factors, including economic, regulatory, scientific, and even social factors make the 1990s the decade during which Green Chemistry was introduced on a wide industrial scale. Since then eco-sustainable solvents and reagents have been widely investigated. In this contest, DMC is a versatile compound which represents an attractive ecofriendly alternative to both methyl halides (or dimethyl sulfate) and phosgene for methylation and carbonylation processes, respectively. DMC, produced nowadays by a clean process, possesses properties of no toxicity, which makes it a true green reagent to be used in syntheses that prevent pollution at the source. The reactivity of DMC is switchable: as it can be used either as methoxycarbonylation or methylation agent with a variety of nucleophiles. Besides, DMC-mediated methylations are catalytic reactions which use safe solids (alkaline carbonates) avoiding the formation of undesirable inorganic salts as by-products. This review reports the latest investigations on DMC focusing on its bench as well as industrial applications

Synthesis of five- and six-membered heterocycles by dimethyl carbonate with catalytic amounts of nitrogen bicyclic bases

Catalytic amount of a nitrogen bicyclic base, i.e., DABCO, DBU and TBD is effective for the one-pot synthesis of heterocycles from 1,4-, 1,5-diols and 1,4-bifunctional compounds via dimethyl carbonate chemistry under neat conditions. Nitrogen bicyclic bases, that previously showed to enhance the reactivity of DMC in methoxycarbonylation reaction by BAc2 mechanism, are herein used for the first time as efficient catalysts for cyclization reaction encompassing both BAc2 and BAl2 pathways. This synthetic procedure was also applied to a large scale synthesis of cyclic sugars isosorbide and isomannide starting from D-sorbitol and D-mannitol, respectively. The resulting anhydro sugar alcohols were obtained as pure crystalline compounds that did not require any further purification or crystallization