A Novel and Regiospecific Synthesis of 1‐Aryl‐1H‐benzotriazoles via Copper(I)‐Catalyzed Intramolecular Cyclization Reaction

1‐Aryl‐1H‐benzotriazole derivatives were synthesized via intramolecular cyclization of easily obtained triazenes, using CuI as the catalyst, DMSO as the solvent, t‐BuONa as the base, and 1,10‐phenanthroline as the ligand, in up to 97% yield. The synthesis is regiospecific and functional group‐tolerant.     

Regiospecific synthesis of 1,2-aminoalcohol by ring-opening of racemic styrene oxide in presence of Lewis acids

The 1,2-aminoalcohol moiety is widely present in compounds possessing pharmaceutically and biologically interesting properties During this work, we targeted the ring opening of the racemic styrene oxide by a chiral amine. In aqueous medium, a mixture of diastereoismers consisting largely of 2-N [1-phenylethyl] amino-1-phenylethanol 1 was obtained. The use of silica in the reaction permits the formation of mixture of diastereoisomers, but, contrary to aqueous solution, the diastereoisomer 2-N [1-phenylethyl] amino-2- phenylethanol 2 was majority. On the other hand, the reaction of ring opening under acidic conditions led to a regiospecific compound, particularly in the presence of Lewis acids, which only leads to the diastereoisomer 2.     

Diastereoselective chain-elongation reactions using microreactors for applications in complex molecule assembly

Diastereoselective chain-elongation reactions are important transformations for the assembly of complex molecular structures, such as those present in polyketide natural products. Here we report new methods for performing crotylation reactions and homopropargylation reactions by using newly developed low-temperature flow-chemistry technology. In-line purification protocols are described, as well as the application of the crotylation protocol in an automated multi-step sequence.     

A method for the synthesis of cyclopropanes by regiospecific and regioselective magnesium carbenoid 1,3-CH insertion as the key reactions

Addition reaction of two geometrical isomers of 1-chlorovinyl p-tolyl sulfoxides, derived from unsymmetrical ketones and chloromethyl p-tolyl sulfoxide, with lithium enolate of tert-butyl acetate gave single diastereomers of the adduct, respectively. Treatment of each diastereomer with i-PrMgCl resulted in the formation of magnesium carbenoid. Highly regiospecific 1,3-CH insertion reaction was found to take place from each magnesium carbenoid to afford cyclopropanes. On the other hand, when the unsymmetrical ketones bearing an oxygen- or a nitrogen-functional group on the α-carbon were used in this procedure, the regioselective 1,3-CH insertion reaction proceeded mainly. Stereochemistry of the adducts, reaction mechanism, and essence of the specificity and the selectivity are discussed.     

Convenient synthesis of trans-3-amino-1-benzylpiperidin-4-ols using regiospecific cleavage of 1-benzyl-3,4-epoxypiperidine with diisobutylaluminum amides (DIBAL-NR1R2)

The report presents a first example of a regio- and stereospecific Lewis acid-catalyzed aminolysis of 1-benzyl-3,4-epoxypiperidine leading to trans-3-amino-1-benzylpiperidin-4-ols, in contrast with other Lewis acid-catalyzed reactions leading to trans-4-amino-1-benzylpiperidin-3-ols. The reaction is performed at room temperature using the reagents prepared by interaction of a hard Lewis acid – diisobutylaluminum hydride (DIBAL-H) with primary and secondary amines. The obtained products are potential intermediates on the way to stereochemical analogues of the antitumor piperidine alkaloid pseudodistomin D.     

A Stereospecific Approach to cis-anti-cis Triquinanes

Abstract

A methodology for the synthesis of compounds containing the cis-anti-cis fused triquinane system has been developed starting from tricyclo[5.2.1.0^2,6]deca-4,8-dien-3-(exo)ol 6 involving Ireland ester Claisen rearrangement and intramolecular diazo ketone cyclopropanation reactions as key steps.     

Concise synthesis of prenylated and geranylated chalcone natural products by regiospecific iodination and Suzuki coupling reactions

Four natural chalcones bearing prenyl or geranyl groups, i.e., isobavachalcone (1), bavachalcone (2), xanthoangelol (3), and 2′,4′,4-trihydroxy-5′-geranylchalcone (isoxanthoangelol, 4) were synthesized by using a regio-selective iodination and the Suzuki coupling reaction as key steps. Among them, the first total synthesis of 2′,4′,4-trihydroxy-5′-geranylchalcone was achieved in 36% overall yield. Comparing with the reported methods based on C-alkylation or O-alkylation followed by Claisen rearrangement to introduce the side chain, this new strategy capitalizes on a precious regiochemical control during iodination. The overall yields for the synthesis of the first three chalcones were improved from 17% to 53%, 12% to 35%, and 28% to 50%, respectively.