Search

A new protocol for the diasteroselective synthesis of pyrrolidin-2-ones 4–14 is presented. Aquivion PFSA effectively catalyzed the diasteroselective nitro-mannich/lactamization cascade reaction between the imine formed from aldehydes 1a–g and amines 2a–b with methyl 3-nitropropanoate 3. The use of flow conditions allow a very efficient waste minimization confirmed by representative green metrics calculations.

A powerful, novel approach to meroterpenes conicol, epiconicol and didehydroconicol has been achieved via a key step Diels–Alder reaction of ( E )-3-methyl-1-(2′,5′-dimethoxyphenyl)buta-1,3-diene as diene with methyl vinyl ketone, methyl acrylate or methyl propiolate as dienophiles. Activation by high pressure (9 kbar) or by the use of Lewis acid catalysts, allows the Diels–Alder reaction to proceed in excellent yield and diastereoselectively to form cyclohexenyl-benzene cycloadducts, which are useful precursors for conicols. The successful total syntheses of conicol, epiconicol and didehydroconicol, are described.

A clean and efficient protocol for the synthesis of a wide variety of N-Boc-s-amino ketones 3a-g has been defined using flow approach. The multistep procedure is based on the s-azidation of unsaturated ketones, consecutive reduction of the azido group, and concomitant amino group protection, and furnishes the desired products in good yields and very low E-factors ranging from 3.1 to 5.6. In batch conditions and by water as reaction medium, poorer yields and complicated reaction mixtures are obtained. Adoption of the flow approach, which combines transformations performed in solvent-free conditions and in EtOAc, has been essential in order to avoid side reactions, poisoning of the reduction catalyst, and use of minimal amount of reactants.

Highly cross-linked imidazolium-based materials, obtained by radical oligomerization of bis-vinylimidazolium salts in the presence of 3-mercaptopropyl-modified silica gel, were used as supports for palladium catalysts. Thanks to the high imidazolium loading these materials were able to support a high amount of the metal (10 wt%). Such materials were characterized by several techniques (13C magic angle spinning nuclear magnetic resonance, the Brunauer-Emmett-Teller technique, X-ray photoelectron spectroscopy, and transmission electron microscopy). The palladium catalysts displayed good activity allowing the synthesis of several biphenyl compounds in high yields working with only 0.1 mol% of palladium loading at 50°C in ethanol/water under batch condition. Moreover, a flow apparatus, to optimize the efficiency of the isolation of the pure products and minimize waste (E-factor), was investigated. For the first time the palladium catalyst and base (K 2CO3) were placed in two separate columns allowing an easy recovery of the products with very low E-factor values (

An efficient protocol for the synthesis of β-amino acids starting from easily accessible α,β-unsaturated carboxylic acids based on the combination of two heterogeneous catalytic systems is reported. This multistep approach is based on the direct β-azidation of α,β-unsaturated carboxylic acids and subsequent azido group reduction performed in flow conditions. It has been demonstrated that the catalysts can be easily recovered and reused conserving its complete efficiency. The green metrics calculations proved the high environmental efficiency of the protocol characterized by very low waste production.

via azidolysis of epoxides under solvent-free conditions in the presence of a polystyrene-supported bisfluoride DABCO catalyst

3-Mercaptopropyl-modified silica-supported bis-imidazolium Pd-catalysts are developed and successfully utilized for Suzuki reactions.

Under solvent-free conditions the reaction of epoxides 1a–i with trimethylsilylazide (2) catalyzed by polystiryl-supported fluoride (PS-DABCOF2) has led to the efficient preparation of the corresponding O-TMS protected 1,2-azido alcohols 3a–i that, by treatment with Dowex-H, gave the related 1,2-azido alcohols 4a–i in excellent yields (83–99% and 82–96%, respectively). The use of a flow procedure has allowed us to significantly minimize waste in the preparation of representative 1,2-azido alcohols 4a, 4c and 4i that have been obtained with E-factors of 1.6, 2.1, and 1.9, respectively. The 1,2-amino alcohols 5a, 5c and 5f have been also prepared, in quantitative yields, by reduction of the corresponding O-TMS protected 1,2-azido alcohols 3a, 3c, and 3f by Pd on the Al2O3/HCOOH system.

Lewis acid catalyzed addition of butadienes to benzylideneacetones at high pressure allows an efficient access to arylated cyclohexenes.