Claudio C. Silveira

Green chemistry: os 12 princípios da química verde e sua inserção nas atividades de ensino e pesquisa

Green chemistry ¾ defined as the design, development, and application of chemical processes and products to reduce or eliminate the use and generation of substances hazardous to human health and the environment. This article summarizes the 12 principles of green chemistry, describing how they have been applied to the academic, industrial and research activities around the world.Green chemistry ¾ defined as the design, development, and application of chemical processes and products to reduce or eliminate the use and generation of substances hazardous to human health and the environment. This article summarizes the 12 principles of green chemistry, describing how they have been applied to the academic, industrial and research activities around the world.

A solvent- and metal-free synthesis of 3-chacogenyl-indoles employing DMSO/I2 as an eco-friendly catalytic oxidation system.

Herein, we describe a solvent- and metal-free method for the synthesis of 3-chalcogenyl-indoles from indoles and diorganyl dichalcogenides using an equivalent amount of DMSO as an oxidant, under catalysis by molecular iodine. This mild and eco-friendly approach allowed the preparation of a wide range of 3-selenyl- and 3-sulfenyl-indoles in good to excellent yields.

Chiral diselenide ligands for the asymmetric copper-catalyzed conjugate addition of Grignard reagents to enones

The copper-catalyzed conjugate addition of Grignard reagents to enones in the presence of chiral diselenide oxazoline ligands has been studied and found to provide good yields and useful levels of asymmetric induction.

Facile and practical enantioselective synthesis of propargylic alcohols by direct addition of alkynes to aldehydes catalyzed by chiral disulfide–oxazolidine ligands

Abstract The enantioselective alkynylation reaction of aldehydes with alkynes and diethylzinc, catalyzed by chiral disulfide–oxazolidine ligands, provides a simple, practical and inexpensive method to access chiral propargylic alcohols in good yields and satisfactory ees.

Vicinal Difunctionalization of Alkynyl Selenides with Lithium Butylcyano Cuprate and Electrophiles

Abstract Alkynyl selenides react with lithium butycyano cuprate giving an intermediate lithium vinylcyano cuprate, which is trapped with electrophiles to give several classes of vinylic selenides.

Synthesis and anti-inflammatory activity of acetylenic thiophenes

A series of acetylenic thiophene derivatives have been synthesized via Pd-catalyzed coupling reaction of 2-(butyltelluro)thiophene with a variety of terminal alkynes. These compounds showed good anti-inflammatory activity in the carrageenin-induced paw edema assay on rats.

New acetylenic furan derivatives: synthesis and anti-inflammatory activity

Abstract A series of acetylenic furan derivatives have been synthesized via Pd-catalyzed coupling reactions of 2-(alkyltelluro)furan with several terminal alkynes. These compounds showed good anti-inflammatory activity in the carrageenin-induced rat paw edema assay. This represents a new and efficient method for the synthesis of pharmacologically active compounds.

A new functionalized, chiral disulfide derived from (L)-cysteine: R,R-bis[(3-benzyloxazolan-4-yl)-methane] disulfide as a catalyst in the diethylzinc addition to aldehydes

Abstract A new, easily accessible, chiral disulfide 3 was prepared from l -cysteine in a short synthetic sequence ( Scheme. 1 ) and applied successfully as a highly efficient catalyst for the enantioselective addition of diethyl zinc to aromatic and aliphatic aldehydes to afford the product alcohols in up to more than 99% ee. In contrast to the more common amino alcohols used in similar reactions, catalyst 3 does not have a protic hydrogen in the form of a free hydroxy group.

Stereoselective addition of sodium organyl chalcogenolates to alkynylphosphonates: synthesis of diethyl 2-(organyl)-2-(organochalcogenyl)vinylphosphonates

Abstract Organyl thiolate, selenolate or tellurolate anions reacted with alkynylphosphonates 1 to give diethyl 2-(organyl)-2-(organochalcogenyl)vinylphosphonates [β-organochalcogenyl vinylphosphonates] 2 in satisfactory yields. The reaction was stereoselective, giving predominantly or exclusively the ( Z ) - stereoisomer.

Synthesis of ketene (S, Te)acetals and their transformation into Z-α-phenylthio-α,β-unsaturated aldehydes

Abstract Reaction of thiomethyl phosphonates with aryl (or butyl) tellurenyl halides and aldehydes under basic conditions provides moderate to good yields of ketene thio (telluro) acetals, with vinylic sulfides being byproducts of this transformation. Tellurium-lithium exchange by reaction with n-BuLi yielded vinyl organolithium species, which were captured with several electrophiles. In the case of DMF, Z-α-phenylthio-α,β-unsaturated aldehydes were obtained.