Chunbao Li

Synthesis of methylenebisamides using CC- or DCMT-activated DMSO

Summary Bisamides are key fragments for the introduction of gem-diaminoalkyl residues into retroinverso pseudopeptide derivatives and in the synthesis of peptidomimetic compounds. The literature methods for these types of compounds have certain drawbacks. In particular, when amides react with electrophile-activated DMSO, the yields are rather low. We have found new electrophiles, 2,4,6-trichloro[1,3,5]triazine (CC) and 2,4-dichloro-6-methoxy[1,3,5]triazine (DCMT), which activate DMSO in the presence of amides to yield methylenebisamides in good to fair yields. The amides can be aromatic or aliphatic. The operation is simple and the reagents are inexpensive.

A Practical solution for aqueous reactions of water-insoluble high-melting-point organic substrates

A practical solution to the problem of performing aqueous reactions for very sparingly soluble high-melting-point (VSSHMP) organic substrates has been developed, which entails mechanically stirring a mixture of the substrate, the corresponding reagent(s), water, catalytic Aliquat 336 and sand. When the melting points of the substrates which include steroids, ketones, aldehydes, aromatics and alkaloids are around 200 °C, the reactions can be performed at 20 °C. The substrate solubility can be as low as 1 × 10−10 mol L−1.

One-Pot Formylation and Dimerization of p-Alkyl Phenols Using DCMT-Activated DMSO

Abstract Dimerization and formylation of p-alkyl-substituted phenols have been successfully achieved in one pot, using 2,4-dichloro-6-methoxy[1,3,5]triazine (DCMT)-activated dimethylsulfoxide. Similarly, the d5-labeled products have been prepared in high selectivity. To the best of our knowledge, the products are of new skeletons, which have not been reported to date. A plausible mechanism is proposed based on the experiments. GRAPHICAL ABSTRACT

One-Pot Synthesis of Oxime Ethers from Benzaldehyde or Acetophenone, Hydroxylamine Salt, Potassium Hydroxide, and Alkyl Halides

Abstract Oxime ethers were synthesized in one-pot reaction from benzaldehyde or acetophenone, hydroxylamine hydrogen chloride, alkyl halides and KOH in aqueous DMSO. The reactions were completed in 15–50 min with yields in 80–96%.

Economical and efficient aqueous reductions of high melting-point imines and nitroarenes to amines: promotion effects of granular PTFE

The reductions of high melting-point imines and nitroarenes to amines in aqueous media using Zn powder, granular PTFE (polytetrafluoroethylene), catalytic Aliquat 336 and NH4Cl or 5% NaOH at room temperature have been achieved. A major advantage of this procedure is that the cost of the catalyst is only 1/7200 of that of a previously reported nitroaromatic aqueous reduction catalyst. Altogether 13 imines and 11 nitroarenes were reduced to the corresponding amines with excellent yields. The effects of the amount of granular PTFE, and solubilities and melting points of the substrates, and melting points of the products on the reaction rates are discussed. For the first time, the relationship between the aqueous reaction rates and melting points of the products was investigated, which leads to a conclusion that lower melting-point products form faster than higher melting-point ones in the aqueous reductions. The Aliquat 336, granular PTFE and water are all recyclable.

A New Method of Introducing SCH3 and SCD3 Groups to Phosphorothioates

Abstract A new synthesis of phosphorothioates starting from phosphites and cyanuric chloride (TCT)-activated DMSO is reported herein. This method enables the incorporation of SCH3 and SCD3 groups into phosphorothioates in good yields. The labeling purities of the products are excellent. GRAPHICAL ABSTRACT

Practical aqueous reactions leading to skeletally diverse carbohydrate-derived ketones

Four types of skeletally diverse compounds have been synthesized from protected aldosyl hemiacetals and methyl ketones using cheap catalysts in water in one pot. Among the four skeletons, two of them are not accessible by current methods. The reactions are operationally simple, high yielding and scalable, which opens a practical channel for utilizing carbohydrates to produce chemical and pharmaceutical intermediates and products.

A protecting group-free synthesis of the antineoplastic agent combretastatin A4

The synthesis of combretastatin A4 (CA4) from commercially available inexpensive materials has been achieved via the Wittig reaction followed by irradiation of the (Z)/(E)-CA4 reaction mixture with sunlight. The method resulted in (Z)-CA4 in high yield. This method does not require protection of the phenolic hydroxy group. The synthesis is operationally simple and cost-efficient.

TEMPO-Catalyzed Direct Conversion of Primary Alcohols to α-Chloroacetals with TCCA Both as an Oxidant and a Chlorination Reagent

Multistep reactions are often required for the transformation of alcohols to α-chloroacetals via the unstable intermediates aldehydes or α-halo aldehydes. Herein, we report a simplified procedure for practical synthesis of α-chloroacetals using 2,2,6,6-tetramethylpiperidine-1-oxyl as a catalyst and trichloroisocyanuric acid both as an oxidant and a chlorination reagent. The reaction is one-pot, solvent-free and high-yielding. In addition, the α-chloroacetals have been transformed to enol ethers through the elimination reaction in the presence of sodium.

A green synthesis of highly substituted 1,5-diketones

Highly substituted 1,5-diketones have been synthesized in water via the reactions between aryl methyl ketones and aldehydes and the subsequent dimerizations. The reaction was catalyzed by aqueous KOH. The advantages of these aqueous reactions over organic-solvent mediated reactions are better yields, better diastereoselectivities, faster reaction rates, simpler workups, and being more energy efficient. The reaction can be scaled up to 13.9 gram scale and the aqueous KOH can be reused for five cycles. A possible mechanism is proposed to explain the high diastereoselectivities.