Synthesis of a Selenium-Substituted Diselenide

Abstract

A wide range of diselenides as precursors for selenium electrophiles is already known, but the development of reagents with higher selectivity is still ongoing. Herein we report the first synthesis of selenium-stabilized diselenides together with some preliminary reactions of these reagents in stereoselective selenenylation reactions.     

Iodine monochloride-amine complexes: an experimental and computational approach to new chiral electrophiles

Lactonizations are important steps in many synthetic sequences. Substrate-controlled reactions that use chiral auxiliaries or chiral alkenes have already been studied in depth. This study focuses on stereoselective reagent-controlled iodolactonizations, by application of a new method that uses complexes of iodine monochloride and various donor molecules. (R)-1,2,3,4-Tetrahydro-1-naphthylamine and other amines with similar structures were found to be efficient in the iodocyclization of 4-aryl-4-pentenoic acids. Calculations were performed on complexes of (R)-1,2,3,4-tetrahydro-1-naphthylamine with XCl (X = I, H) to identify possible reactive species in these iodocyclizations. Calculations were carried out at various levels of theory, including B3 LYP/6-31+G (d,p) by using a modified SDD basis set for iodine.     

烯基碲化合物的合成及其在烯烃立体选择合成反应中的应用

综述了近年来烯碲化合物的合成及其在立体选择合成中的应用。参考文献49篇。     

Dynamic Kinetic Resolution Approach for the Asymmetric Synthesis of Tetrahydrobenzodiazepines Using Transfer Hydrogenation by Chiral Phosphoric Acid

Asymmetric synthesis of tetrahydrobenzodiazepines was achieved by transfer hydrogenation of dihydrobenzodiazepines with benzothiazoline having a hydrogen‐bonding donor substituent by means of a newly synthesized chiral phosphoric acid. This method was applicable to various racemic dihydrobenzodiazepines to give the corresponding products in good yields with excellent diastereoselectivities and enantioselectivities taking advantage of the dynamic kinetic resolution. Furthermore, the effect of bulky substituent at 3,3′‐position on the catalyst and hydrogen‐bonding donor substituent on benzothiazoline was fully elucidated by the theoretical study.     

An Efficient Approach to Chiral Allyloxyamines by Stereospecific Allylation of Nitrosoarenes with Chiral Allylboronates

A novel and efficient approach to allyloxyamines by the allylation of nitrosoarenes with α‐chiral allylboronates is described. C? O bond formation occurs with high stereospecificity and the product allyloxyamines are easily transformed into valuable chiral building blocks such as isoxazolidines and allylic alcohols. The reaction features complete regioselectivity (O‐selectivity), high E/Z selectivity, and excellent chirality transfer.     

Stereospecific Formal [3+2] Dipolar Cycloaddition of Cyclopropanes with Nitrosoarenes: An Approach to Isoxazolidines

The MgBr₂‐catalyzed formal [3+2] cycloaddition of donor–acceptor activated cyclopropanes with nitrosoarenes offers a novel approach to various structurally diverse isoxazolidines. The reactions, which are experimentally easy to conduct, occur with complete stereospecificity and perfect control of regioselectivity. Product isoxazolidines can be readily transformed into α‐amino lactones by reductive or decarboxylative N? O cleavage and subsequent lactonisation, and the N‐aryl bond cleavage is also possible under oxidative conditions.     

Copper‐Catalyzed Formal [2+2+1] Heteroannulation of Alkenes,Alkylnitriles, and Water: Method Development and Application to a Total Synthesis of (±)‐Sacidumlignan D

A copper‐catalyzed three‐component reaction of alkenes, alkylnitriles, and water affords γ‐butyrolactones in good yields. The domino process involves an unprecedented hydroxy‐cyanoalkylation of alkenes and subsequent lactonization with the creation of three chemical bonds and a quaternary carbon center. The synthetic potential of this novel [2+2+1] heteroannulation reaction was illustrated by a concise total synthesis of (±)‐sacidumlignan D.     

Stereoselective Ketone Rearrangements with Hypervalent Iodine Reagents

The first stereoselective version of an iodine(III)‐mediated rearrangement of arylketones in the presence of orthoesters is described. The reaction products, α‐arylated esters, are very useful intermediates in the synthesis of bioactive compounds such as ibuprofen. With chiral lactic acid‐based iodine(III) reagents product selectivities of up to 73 % ee have been achieved.     

Stereoselective synthesis of (+)-1-deoxyaltronojirimycin

A stereocontrolled, facile and high-yield approach for producing (+)-altroDNJ, has been developed starting from the inexpensive commercial cis 2-butene-1,4-diol. Sharpless epoxidation and a subsequent dihydroxylation were used for the introduction of all stereocentres; finally, the ring closure under basic conditions afforded the piperidine heterocycle.     

Improved one-pot synthesis of styryl tetrahydrofurans and cyclohexanes by radical addition to beta-nitrostyrenes in the presence of benzoyl peroxide

Stereoselective styryl derivatives have been prepared based on radical substitution (addition-elimination) of heterocycles or cyclohydrocarbons units to (E)-beta-nitrostyrenes 1 using a common radical initiator benzoyl peroxide. High reactivity and selectivity with wide substrate scope were attained by using this easy methodology. The reactions using easily obtained and one-pot potential starting materials gave excellent trans-selectivity with medium to high yields in all cases. Synthetic utility of this approach has been demonstrated by the preparation of various trans-styryl derivatives.     

Planar Chiral Dialkoxysilane: Introduction of Inherent Chirality and High Reactivity in Conventional Achiral Alkene

A simple eight‐membered dialkoxysilane (E)‐ 1 prepared from 2‐pentene‐1,5‐diol, showed remarkably stable planar chirality along with high reactivity toward epoxidation, Diels–Alder reaction, and cycloaddition reaction with azide.     

Synthetic and DFT Studies Towards a Unified Approach to Phlegmarine Alkaloids: Aza‐Michael Intramolecular Processes Leading to 5‐Oxodecahydroquinolines

A diastereoselective synthesis of cis‐5‐oxodecahydroquinolines is described in which three stereocenters are generated in a one‐pot reaction. The reaction involves a lithium hydroxide‐promoted Robinson annulation/intramolecular aza‐Michael domino process from an achiral acyclic tosylamine‐tethered β‐keto ester. The development and scope of this reaction was facilitated through the use of DFT‐based mechanistic studies, which enabled the observed diastereodivergent course of the azacyclization to be rationalized. The varying stereochemistry and stability of the resulting decahydroquinolines was found to depend on whether a β‐keto ester or ketone were embedded in the substrates undergoing aminocyclization. This synthetic approach gave access not only to both diastereomeric cis‐decahydroquinolines from the same precursor, but also to the corresponding trans isomers, through an epimerization processes of the corresponding N‐unsubstituted cis‐5‐oxodecahydroquinolines. The described methodology provides advanced building‐blocks with the three relative stereochemistries required for the total synthesis of phlegmarine alkaloids.     

Cyclization of Homopropargyl Chalcogenides by Copper(II) Salts: Selective Synthesis of 2,3‐Dihydroselenophenes, 3‐Arylselenophenes,and 3‐Haloselenophenes/thiophenes

Copper(II) halide mediated cyclization of homopropargyl chalcogenides gave three types of chalcogenophene derivatives. Selective product formation was achieved by controlling solvent, temperature, and atmosphere. By using CuBr₂ and 1,2‐dichloroethane at room temperature under ambient atmosphere, 4‐bromo dihydroselenophene derivatives were obtained, whereas CuBr₂ and 1,2‐dichloroethane at reflux gave selectively 2‐substituted selenophenes. When 1,2‐dichloroethane was replaced by dimethylacetamide, 3‐halo‐selenophenes were obtained exclusively. The versatility of chalcogenophenes was also studied by reaction of 3‐haloselenophenes with terminal alkynes under Sonogashira conditions affording the cross‐coupled products. In addition, the reaction of 3‐haloselenophenes with boronic acids gave the corresponding Suzuki‐type products in good yields.