Base-Mediated Transition-Metal-Free Dehydrative C-C and C-N Bond-Forming Reactions from Alcohols.

In recent years, there has been an increasing interest in using alcohols as alkylating agents for C-C and C-N bond-forming processes employing mainly TM-catalysts. Although BH-catalysis looks like a green atom economy process since water is the only by-product, it often suffers from one or more drawbacks, such as the use of expensive noble metal complexes, capricious ligands, and toxic organic solvents. Therefore, straightforward, efficient, atom economy and environmentally benign alternative protocols are desirable.

Synthesis of Quinolines via a Metal-Catalyzed Dehydrogenative N-Heterocyclization.

Efficient ruthenium-, rhodium-, palladium-, copper- and iridium-catalysed methodologies have been recently developed for the synthesis of quinolines by the reaction of 2-aminobenzyl alcohols with carbonyl compounds (aldehydes and ketones) or the related alcohols. The reaction is assumed to proceed via a sequence involving initial metal-catalysed oxidation of 2-aminobenzyl alcohols to the related 2-aminobenzaldehydes, followed by cross aldol reaction with a carbonyl compound under basic conditions to afford α,β-unsaturated carbonyl compounds. These aldehydes or ketones can be also generated in situ via dehydrogenation of the related primary and secondary alcohols.

Recent advances in osmium-catalyzed hydrogenation and dehydrogenation reactions.

CONSPECTUS: A current issue in metal-catalyzed reactions is the search for highly efficient transition-metal complexes affording high productivity and selectivity in a variety of processes. Moreover, there is also a great interest in multitasking catalysts that are able to efficiently promote different organic transformations by careful switching of the reaction parameters, such as temperature, solvent, and cocatalyst. In this context, osmium complexes have shown the ability to catalyze efficiently different types of reactions involving hydrogen, proving at the same time high thermal stability and simple synthesis.

Stereospecific hydrodehalogenation of alkenyl bromides: a new approach to the synthesis of (E)-alkenes.

The pair NaBH4-TMEDA and catalytic PdCl2(PPh3)2 in THF at room temperature is a mild and efficient system for the hydrodebromination of alkenyl bromides, providing a facile reduction procedure that allows completing the process advantageously, leading from aldehydes to (E)-alkenes.

Synthesis of tricyclic condensed rings incorporating the pyrazole or isoxazole moieties bonded to a 4-piperidinyl substituent.

In this paper we report the synthesis of new compounds based on the pyrazole and isoxazole framework fused to a cycloalkene unit, and bearing as a substituent the 1-piperidinyl group as new examples of potential antipsychotic molecules. The general synthesis involves the acylation of a chloro-substituted cyclic ketone with a 1-substituted piperidine-4-carboxylate derivative, followed by heterocyclization of the formed 1,3-dioxo compound with a hydrazine or hydroxylamine.