JAMES LESLIE CHAXLTON, HOI KIONG LAI, and GERALD NICHOLAS LYPKA. Can. J. Chem. 58,458 (1980). Earlier work on the photochemistry of a-sulfonyloxyketones uncovered their propensity to form the corresponding a-keto carbonium ions on photolysis. Typical reactions such as intramolecular cyclizations, carbonium ion rearrangements, and solvent trapping were found. This paper describes an attempt to extend this reaction to a general synthetic technique for polyene cyclizations. During the course of this work two other major reaction pathways were found. The first is an a-keto carbonium ion to acylium ion rearrangement and the second is a photoreduction-elimination process that leads to an a-keto radical rather than the corresponding cation. Chem. 58.458 (1980). Des travaux anterieurs sur la photochimie des a-sulfonyloxycetones ont permis de mettre en evidence leur tendance aformer les ions a-ceto carbonium par photolyse. On a trouve des reactions typiques telles que des cyclisation intramoleculaires, des transpositions de l'ion carbonium et sa capture par le solvant. Cette publication decrit une tentative d'etendre cette reaction a une technique generale de synthese pour la cyclisation des polyenes. On a trouve au cours de ce travail deux autres voies principales pour la reaction. La premiere est une transposition d'un ion a-ceto carbonium en un ion acylium et la deuxieme un procede de photoreduction-elimination qui conduit au radical a-cetonique plut8t qu'au cation correspondant.[

The photochemistry of 4-phenyl-1-iodobutane 3 and 4-phenyl-2-iodomethyl-1-butene 4 has been studied to investigate the effect of structure on the character of the intermediates generated on photolysis. The irradiation of the simple primary iodide 3 appears to yield only radical intermediates. By contrast the photolysis of the allylic iodide 4 yields products that are more consistent with cationic intermediates.

The anthracycline antibiotics daunorubicin and adriamycin are potent antitumor agents. It has recently been suggested that 5-oxaanthracycline analogs of these compounds might show reduced cardiotoxicity, a property that limits the clinical use of the anthracyclines. In this paper we describe the condensation–cyclization reactions of 2-methylchromone-3-carboxylate with cyclohexanones, a reaction that leads ultimately to the xanthocycline skeleton.

N-tert-Butyldimethylsilyl derivatives of imidazole, 2-methylimidazole, 4-methylimidazole, benzimidazole, pyrazole, 1,2,4-triazole, and benzotriazole were prepared from tert-butyldimethylsilyl chloride and the corresponding heterocyclic compound. The products were identified by carbon and proton nmr, mass spectrometry, and elemental analysis. The carbon nmr spectra confirmed the absence of intermolecular silyl exchange at ambient temperature. Silyl exchange did occur at elevated temperatures, 130–160 °C.Reaction of N-tert-butyldimethylsilyl or N-trimethylsilyl heterocycles with dimethylsulfoxide gave N-(methylthio)methyl derivatives of imidazole, 2-methylimidazole, 4-methylimidazole, benzimidazole, pyrazole, and 1,2,4-triazole. The products were characterized by carbon and proton nmr, mass spectrometry, and elemental analysis. A mechanism involving a Pummerer rearrangement is proposed to account for the results.

N‐[(Methylthio)methyl]imidazole may be prepared from dimethylsulfoxide and N‐(trimethylsilyl)imidazole or N‐(t‐butyldimethylsilyl)imidazole at elevated temperatures via a Purnmerer rearrangement. The product was characterized by elemental analysis, mass spectrometry and proton and carbon nmr. Preliminary experiments show that corresponding derivatives of 2‐methylimidazole, pyrazole, triazole and benzimidazole may also be prepared in an analogous manner.