Ethylboration of Stannyl-Substituted Sulfur Diimides

Abstract Bis(sulfurdiimido)tin compounds of the type R2Sn[(NSN)tBu]2 [R = Me (2a), Et (2b)] re act with triethylborane Et3B by rearrangement and N-ethylation to give the novel aminoborane derivatives R2Sn[N(tBu)SN(Et)BEt2]2 (5a, b), in the same way as nBu3Sn(NSN)tBu (1) reacts with Et3B to give nBu3Sn[N(tBu)SN(Et)BEt2] (4). In contrast, 2c (R = tBu) and tris(sulfurdiimido)tin compounds RSn[(NSN)tBu]3 [R = Me (3a), nBu (3d)] react with Et3B mainly by Sn- and S-ethylation, accompanied by extensive decomposition. 1H, 11B , 13C, 15N and 119Sn NMR spectroscopy served for the structural assignment in solution.

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Ten-Vertex Polyhedral Monocarbaborane Chemistry. The Novel High-Yield Formation of the Ten-Vertex closo Compound [6-(PMe2Ph)-closo-1-CB9H9] from the Thermolysis of [8,8-(PMe2Ph)2-nido-8,7-PtCB9H11]

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19932924 ◽

1993 ◽

Vol 58 (12) ◽

pp. 2924-2935 ◽

Cited By ~ 8

Author(s):

Jane H. Jones ◽

Bohumil Štíbr ◽

John D. Kennedy ◽

Mark Thornton-Pett

Keyword(s):

Nmr Spectroscopy ◽

Diffraction Analysis ◽

High Yield ◽

Monoclinic Space Group ◽

The Novel ◽

X Ray Diffraction ◽

Metal Centre ◽

X Ray ◽

Yield Formation ◽

Boiling Toluene

Thermolysis of [8,8-(PMe2Ph)2-nido-8,7-PtCB9H11] in boiling toluene solution results in an elimination of the platinum centre and cluster closure to give the ten-vertex closo species [6-(PMe2Ph)-closo-1-CB9H9] in 85% yield as a colourles air stable solid. The product is characterized by NMR spectroscopy and single-crystal X-ray diffraction analysis. Crystals (from hexane-dichloromethane) are monoclinic, space group P21/c, with a = 903.20(9), b = 1 481.86(11), c = 2 320.0(2) pm, β = 97.860(7)° and Z = 8, and the structure has been refined to R(Rw) = 0.045(0.051) for 3 281 observed reflections with Fo > 2.0σ(Fo). The clean high-yield elimination of a metal centre from a polyhedral metallaborane or metallaheteroborane species is very rare.

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Synthesis, characterization, and enzymic conversion of nonhydrolysable analogues of propionylcoenzyme A

Canadian Journal of Chemistry ◽

10.1139/v94-025 ◽

1994 ◽

Vol 72 (1) ◽

pp. 164-169 ◽

Cited By ~ 7

Author(s):

Yimin Zhao ◽

Martina Michenfelder ◽

János Rétey

Keyword(s):

Mass Spectrometry ◽

Nmr Spectroscopy ◽

Coenzyme A ◽

The Novel ◽

Mechanistic Studies ◽

Preparative Scale ◽

Propionibacterium Shermanii ◽

Fab Mass Spectrometry ◽

Michaelis Constants ◽

Coenzyme B

We describe the synthesis of three novel analogues of propionyl-coenzyme A, in which the sulfur atom has been replaced by methylene, ethylene, and thiomethylene, respectively. All three analogues, propionyl-dethia(carba)-CoA (1), propionyl-dethia(dicarba)-CoA (2), and S-(2-oxobutanyl)-CoA (3) were characterized by 1H and 31P NMR spectroscopy and FAB mass spectrometry. Propionyl-CoA–oxaloacetate transcarboxylase from Propionibacterium shermanii accepted the novel analogues as substrates and carboxylated them to the corresponding methylmalonyl-CoA analogues (4–6). The latter were further converted into the succinyl-CoA analogues by the coenzyme-B12-dependent methylmalonyl-CoA mutase from the same organism. The succinyl-CoA analogues, succinyl-dethia(carba)-CoA (7), succinyl-dethia(dicarba)-CoA (8), and 4-carboxy(2-oxobutanyl)-CoA (9) were obtained on a preparative scale and their Michaelis constants (Km) with methylmalonyl-CoA mutase were determined to be 0.136, 2.20, and 0.132 mM, respectively (Km for succinyl-CoA is 0.025 mM). The Vmax values for 7, 8, and 9 are 1.1, 0.013, and 0.0047 µmol min−1 U−1, respectively (Vmax for succinyl CoA is 1.0). The utility of the novel coenzyme A analogues in enzyme mechanistic studies is discussed.

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