Selenium-containing amines

Bansal et al. found that the recently synthesized phosphatriazolo[l,5- ]pyridines can undergo addition reaction on the phosphorus atom when treated with sulfur or selenium in the presence of a secondary amine <1995ZNB558> (Scheme 15). Thus, reaction of 4 with these reagents yields under mild conditions the sulfur- or selenium containing addition products 51a and 51b in fair yield. 

Selenium-containing six-membered ring heterocycles have proved to be useful catalysts in a variety of transformations. The Baylis-Hillman reaction involves the reaction of alkenes containing electron-withdrawing groups such as a,/3-unsaturated carbonyl compounds with aldehydes leading to carbon-carbon bond formation (Equation 79). The reaction is promoted by tertiary amines such as l,4-diazabicyclo[2.2.2]octane (DABCO), or tertiary phosphines and Lewis acids. Unfortunately, the Baylis-Hillman reaction is severely limited because it proceeds only very slowly <1998CC197>. Much research has been carried out in attempts to increase the rate of this reaction. 

Elemental selenium is an excellent catalyst for fhe carbonylation of a variety of nucleophiles such as amines, alcohols, water, and carbon nucleophiles in the presence of oxygen under mild conditions [114]. In fhe synfhesis of ureas from primary amines and CO, for example (Scheme 15.42), the turnover number reaches ca. 10", giving ureas in almost quantitative yields. Successful applications of this Se/CO system include not only synfhetic reactions with a variety of carbamates, carbonates, and sulfur- or selenium-containing compounds but also metallurgical refining of selenium and several important processes as exemplified by isocyanate synfhesis, fhe water-gas shift reaction, and separation of carbon monoxide [115]. 

Series of selenium-containing phosphorus compounds (137-139) have been reported by Kimura and Murai. Phosphinoselenoic amides 137 were prepared from racemic phosphinoselenoic chlorides (138) and chiral amines and the individual isomers could be separated by column chromatography in some cases.Reaction of 137 with tributylphosphine afforded the P(III) aminophosphines with retention of configuration at the phosphorus atom. (5)-methylbenzylamine was also used to prepare both enantiomers of phosphinoselenoic chlorides 138 in 96% ee. In contrast to the oxygen analogues, they were found to be stable and could be purified by column chromatography. Several compounds, such as 139 for example, were prepared by stereoselective nucleophilic substitutions of the Cl atom. ... 

Andrade, L.H., Silva, A.V., and Pedrozo, E.C. (2009) First dynamic kinetic resolution of selenium-containing chiral amines catalyzed... 

In 2009, Andrade et al. demonstrated that the DKR mediated by palladium and lipase could be efficiently applied to selenium-containing amines. As shown in Scheme 4.55, a series of organoselenium-l-phenylethanamines were submitted to DKR catalysed by a combination of Pd/BaS04 and Candida... 

The selenium-containing ring (428) can be prepared by the action of hydrogen selenide on the appropriate amine with formaldehyde in aqueous ethanol,and n.m.r. data reveal that the action of RP(NEt)2 (R = Me,... 

In some reactions intramolecular chalcogen nitrogen interactions may lead to stereochemical control. For example, selenenyl bromides react with C=C double bonds, providing a convenient method of introducing various functional groups. The reaction proceeds readily, but affords a racemic mixture. The modified reagent 15.22 contains a chiral amine in close interaction with the selenium atom. It reacts with olefins affording up to 97% ee of isomer A (Scheme 15.2). ... 

This ch ter contains reactions which prepare the oxides of nitrogen, sulfur and selenium. Included are W-oxides, nitroso and nitro compounds, nitrile oxides, sulfoxides, selenoxides and sulfones. Oximes are considered to be amines and appear in those sections. Preparation of sulfonic acid derivatives are found in Chapter Two and the preparation of sulfonates in Chapter Ten. 

Ionic liquids have been used for the selenium- or palladium-catalyzed carbonylation of primary amines to form carbamates or ureas.After completion of the carbonylation, addition of water induced the precipitation of desired products, which were isolated by fdtration and separated from the ionic liquid, containing the catalytic species. Then, the catalyst could be reused after removal of residual methanol and water by distillation. Although the conversion of the reaction slightly decreased after the second run, the catalytic activity was considerably improved (from 70% to 99 %) by the addition of a small amount of the fresh catalyst. " ... 

A number of substances, such as the most commonly used sulfur dioxide, can reduce selenous acid solution to an elemental selenium precipitate. This precipitation separates the selenium from most elements and serves as a basis for gravimetry. In a solution containing both selenous and tellurous acids, the selenium may be quantitatively separated from the latter by performing the reduction in a solution which is 8 to 9.5 N with respect to hydrochloric acid. When selenic acid may also be present, the addition of hydroxy] amine hydrochloride is recommended along with the sulfur dioxide. A simple method for the separation and determination of selenium(IV) and molybdenum(VI) in mixtures, based on selective precipitation with potassium thiocarbonate, has been developed (69). 

Alkenes can be aminated172 in the allylic position by treatment with solutions of imido selenium compounds R—N=Se=N—R.173 The reaction, which is similar to the allylic oxidation of alkenes with Se02 (see 4-4), has been performed with R = f-Bu and R = Ts. The imido sulfur compound TsN=S=NTs has also been used.174 In another reaction, compounds containing an active hydrogen can be converted to primary amines in moderate yields by treatment with 0-(2,4-dinitrophenyl)hydroxylamine.175... 

Treatment of a-alkyl and a,a-dialkyl homoallylic amines 209 with phenyl selenium halides (X = C1, Br, I) in acetonitrile containing sodium carbonate produced mixtures of azetidines and pyrrolidines <1997TL1393, 2002EJ0995>. The ratio of azetidine to pyrrolidine increased according to the steric hinderance around the cr-carbon and with the nature of the counterion X (PhSeCl < PhSeBr < PhSel). The mechanistic investigations led to the conclusion that seleniranium halide intermediates 210 were involved in ring closure to azetidines 211 (Scheme 41). 

Owing to the high polarizability of the carbon-selenium double bond, selenoesters can easily be attacked by nucleophiles. This property makes a selenoester a useful reagent for the synthesis of hetero-cycles. Condensation of selenoesters with bifiinctional aromatic or aliphatic amines has yielded a variety of nitrogen-containing heterocyclic compounds (Scheme 19). 

Silastannathianes containing the unit SiSSn can be prepared from the reaction of a mixture of tin halide and silicon halide with hydrogen sulfide in the presence of an amine, and the corresponding selenium and tellurium compounds from a similar reaction using lithium selenide or lithium telluride.14... 

The first chemoenzymatic synthesis of organoselenium containing amines was recently reported by Andrade and Silva (Figure 14.7) [10]. Compounds containing a selenium atom have important antioxidant and anti inflammatory activities. Lipase mediated acylation of amine 13 gave the corresponding chiral amides 14 and amines 13 with excellent enantioselectivity (up to 99% ee). 

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