Selenols

D-glyceric acid + NH amino acid(s) + selenol(s) glycerate dehydrogenase + Ala dehydrogenase 202... 

The 7 a-bromo steroid (9) can also be treated with sodium phenyl selenolate (41). The resultant 7 P-phenyl selenide (13) can be oxidized and the corresponding phenyl selenoxide elirninated to form the 7-dehydtocholesteryl ester (11). 

Metal selenolates of the type M(SeAr)2 (M = Zn, Cd, Hg) are usually insoluble, polymeric compounds. Intramolecular Se N coordination has been employed to stabilize monomeric mercury selenolates, e.g., 15.27, but this approach was not successful for the zinc and cadmium derivatives. ... 

Synthesis of thiols, selenols, sulfides, selenides, sulfoxides, sulfones, and se-lenones of heterocyclic series 98JCS(P1)1973, 99JCS(P1)641. 

Treatment of 2-aminoselenazoline with aqueous alkaline base (63) or with hydrogen sulfide (64) leads to ring rupture and gives 2-ureidoethane-selenol and 2-thioureidoethaneselenol. which are not isolated but give by oxidation l,T-(diselenodiethy ene)-bis(2-thiourea) (H2N-C-NH-CH -... 

Although the oxoacids of selenium and sulfur have comparable acid strengths (pITai 2.6 vs. p fa 1-9, respectively, for the quadrivalent species pA a 3 for both the hexavalent species), the hydride H2Se is much more acidic than H2S (pATai 3.9 vs. 7.0). Thus, while thiols such as cysteine are mainly protonated at physiological pH, selenols such as selenocysteine are predominantly dissociated under the same conditions. 

These reactions could proceed either via (1) insertion of the alkyne or the allene into the M-Se bonds, and (2) C-H bond-forming reductive elimination (or protolysis by selenol) or via (1) insertion of the alkyne or the aUene into the M-H bond, and (2) C-Se bond-forming reductive elimination. 

Hydrozirconation of terminal alkynes R-C=CH (R= aryl, alkyl) with 1 affords terminally ( )-Zr-substituted alkenes with high efficiency and excellent stereochemical and regiochemical control (>98%). These alkenylzirconocene complexes are of particular interest for synthetic use [136, 143, 144]. Moreover, beside the electropositive halogen sources [145] and heteroatom electrophiles [3] used in the pioneering studies to directly cleave the Zr-C bond, ( )-vinyl-Zr complexes were recently transformed into a number of other trans-functionalized alkenes such as ( )-vinyl-sul-fides[146], vinylic selenol esters [147], vinyl-sulfones [148], vinyl-iodonium [149], vinyl-(R0)2P(0) [150], and vinilic tellurides [143]. 

Insertion of a C=0 or C=S group between two thiol or two selenol functions of a 1,2- or 1,3-dithiol or diselenol results in formation of the corresponding five- or six-membered heterocycles. 

Like the three-coordinate aluminum and gallium alkoxides, the corresponding thiolates, selenolates, and tellurolates require very bulky substituents at the chalcogen atom to ensure a low metal coordination number. In addition, the steric requirements associated with the preservation of the low coordination number at the metal are increased by the longer M—S and M—Se bond lengths. The ten examples of low-coordinate,... 

Metal-Sulfur, -Selenium, and -Tellurium Bond Lengths, M—E—C Angles, and Torsion Angles for Three-Coordinate Aluminum, Gallium, and Indium Thiolates, Selenolates and Tellurolates", and Related Compounds... 

Treatment of tetrahydroberberine (26) with sodium benzenethiolate (48) or -selenolate (49) in the presence of ruthenium catalyst afforded the C-14—N bond cleavage products 51 or 52 with a phenylthio or phenylseleno group at C-14 (Scheme 12). The latter was converted to the 10-membered amino olefin 53 on treatment with m-chloroperbenzoic acid. 

In the second step of this reaction the O—O bond of H2O2 is cleaved. During this process, one hydroxyl fragment (0 11) is transferred to the selenolate anion (R—Se-) to form selenenic acid (R—SeO1 II), while simultaneously the second... 

Nickel-selenium coordination compounds have received attention in recent years, because a unique Ni-selenocysteine interaction was revealed in the active site of [FeNiSe]-hydrogenases.1083,1084 Of particular interest in this regard are mixed CO/selenolate complexes. Distorted square planar (393) was prepared from [CpNi(CO)]2, PhSeSePh, and [Fe(CO)3(SePh)3] and provides the first example of CO bound to a square planar Ni11 center in thiolate/selenolate environment.1085,1086 Upon addition of RSSR, species of the series [Ni(CO)(SR) (SePh)3 ] are formed. //(CO) ranges from 2,023 cm-1 to 2,043 cm-1 and is regarded as a spectroscopic reference for the CO binding site in [NiFeSe] hydrogenases. 

In (393), the average Ni—Se distance is 231.7(2) pm.1085 Simple tetrahedral [Ni(SePh)4]2 has been prepared by reaction of NiCl2-4H20 with LiSePh.1087,1088 An excess of selenolate has to be used to prevent formation of [Ni(SePh)2]8. The PPh4+ salt is stable in air for several hours. Its average Ni—Se bond lengths (240.1(3) pm) are longer than in the homoleptic square planar systems. 

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