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APbX3 (A: MeNH3+, Me2NH2+, Me3NH+; X: I, Br) hybrid organic-inorganic compounds are prepared by dissolving appropriate amounts of Pb(O-Ac)2 in excess HX (100 °C) followed by the addition of the respective amine (25—40% in H2O) in stoichiometric quantities and subsequent cooling to 46 °C at a rate of 1 °C/min.

Racemic 4-oxocyclopent-2-en-1-yl acetate was used in a short synthesis of nucleoside analogues with pyrimidine and purine heterobases. The protocol is based on a typical nucleophilic substitution process. Uracil, thymine, 6-chloropurine, and some adenines gave the expected 4-heterosubstituted products along with the isomeric 2-heterosubstituted compounds as minor components. Samples of selected products were evaluated for their antiviral activity in a primary screening against a variety of viruses belonging to different classes. One of the compounds was found to be highly active against human papilloma virus (HPV).

We report the synthesis and characterization of a MASnxPb1-xBr3 (MA = methylammonium; nominal x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) solid solution. The original synthetic method developed allowed one to obtain single-phase materials with homogeneous Sn/Pb distribution. All of the samples prepared are cubic, and the unit cell linearly decreases with increasing x value. The optical response indicates a linear trend (Vegard's law) of the band gap with increasing Sn content from 2.20 eV (x = 0) to 1.33 eV (x = 1), thus extending light absorption into the near-IR.

Addition of N-methyl morpholine N-oxide (NMO) to a nitrile oxide solution in dichloromethane at room temperature in the presence of a diene affords nitroso carbonyl adducts in fair yields.

Nitrosocarbonyl intermediates, generated at r.t. by the mild oxidation of nitrile oxides, undergo clean ene reactions with tetramethyl- and trimethyl-ethylene and with cyclohexene. With less substituted ethylenes the ene pathway is still active but the oxidation step of the nitrile oxides competes with the cycloadditions to the olefins.

Nitroscarbonyl intermediates are photochemically generated from 1,2,4-oxadiazole-4-oxides and efficiently trapped with enes and dienes.

The regiochemistry of the cycloadditions of nitrile oxides to α,β-unsaturated amides is determined by frontier orbital interactions and by a regiochemical drift due to steric effects. Cycloadditions to α,β-unsaturated lactames afford mainly 4-carboxamido-isoxazolines with high regioselectivity. In cycloadditions to acyclic α,β-unsaturated amides the regioselectivity relaxes and finally reverses in the case of N,N-disubstituted derivatives, because of the increasing steric congestion at the amine nitrogen.

Nitrile oxides are oxidized by tertiary amine N-oxides in different solvents at room temperature to afford in the presence of dienes nitrosocarbonyl adducts in fair yields. The mild conditions used in oxidizing a variety of nitrile oxides promise a wide application of this method in synthetic processes.

N-Acyl-2-oxa-3-azanorborn-5-enes are highly reactive dipolarophiles in cycloadditions with nitrile oxides. The cycloadducts can be easily elaborated to various functionalized structures that are not directly accessible by 1,3-dipolar cycloadditions.