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A concise and modular synthesis of phenanthroindolizidine alkaloids was achieved by combining iodoaminocylization with a free radical cyclization approach. The route described allowed the preparation of (±)-tylophorine, (±)-antofine, and (±)-deoxypergularinine in six steps. When commercially available l-prolinol was used as a chiral building block, (S)-(+)-tylophorine was also synthesized in 49% yield and >99% ee over five linear steps. [ABSTRACT FROM AUTHOR]

A general and practical method for the preparation of trans-2-substituted-4-halopiperidines and cis-2-substituted-4-halotetrahydropyrans is reported. Using 5 mol % of AlCl3 as the catalyst and 2 equiv of trimethylsilyl halides as the halide sources, aza-Prins cyclization of N-tosyl homoallylamine or Prins cyclization of homoallylic alcohol with carbonyl compounds could be readily realized, giving the corresponding trans-2-substituted-4-halopiperidines or cis-2-substituted-4-halotetrahydropyrans in high yields and satisfactory diastereoselectivity. [ABSTRACT FROM AUTHOR]

A new method for the construction of oxazoline moiety was detailed. Using (diacetoxyiodo)benzene (PIDA) as the reaction promoter and halotrimethylsilane as the halogen source, intramolecular halooxygenation and halothionation of N-allylcarboxamides/N-allylcarbothioamides proceeded readily, leading to the corresponding 5-halomethyloxazolines/5-halomethylthiazolines in good to excellent isolated yields. The 5-halomethyl products could be converted to different derivatives via conventional nucleophilic substitution methods. The reactions were carried out using easily available starting materials, and did not need harsh reaction conditions. All these features made this reaction a viable method for the construction of different oxazoline and thiazoline structures. [ABSTRACT FROM AUTHOR]

A metal-free method for intramolecular halocyclization of unfunctionalized olefins was detailed. (Diacetoxyiodo)benzene (PIDA) was very effective for haloamidation, haloetherification, and halolactonization of unfunctionalized olefins. In the presence of 1.1 equiv of PIDA and suitable halogen sources, a variety of unfunctionalized olefins could be converted to the corresponding 1,2-bifunctional cyclic skeletons in good to excellent isolated yields, and key intermediates for biologically interesting compounds could be obtained in high yields under mild conditions via nucleophilic substitution of the thus obtained halocyclization products. [ABSTRACT FROM AUTHOR]

Trifluoroacetic acid was found to be effective in intramolecular hydroamination of unfunctionalized olefins bearing electron-rich amino groups, and the corresponding N-heterocycles were obtained in good isolated yields. The scope of the substrates was investigated, and a possible reaction mechanism was proposed. Substituents on CC double bonds and amino groups of the substrates showed drastic effects on the course of the reactions. [ABSTRACT FROM AUTHOR]

Organoselenium compounds, a significant class of substances with applications in the biological, medicinal and material sciences as well as in modern organic synthesis, have attracted considerable attention from the scientific community. Consequently, an intriguing and trending research topic is the development of convenient, efficient, and sustainable methods for forming carbon-selenium (C-Se) bonds to access complex structures from simple starting materials. Over the last decade, electro-organic synthesis has gained recognition as a powerful and environmentally friendly tool for building chemical bonds. In particular, electrochemical selenofunctionalization of unsaturated bonds has emerged as an ideal and powerful route to obtain high-value selenylated products with reduced cost and waste. Thus, we outline recent progress in electrochemically enabled selenofunctionalization of alkenes and alkynes. The scope and limitations of these reactions and mechanisms are thoroughly discussed. [ABSTRACT FROM AUTHOR]