Sulfur , insertion into

Sulfur insertion into thiols RSH to give symmetrical trisulfides in high purity is easily accomplished by diimidazolylsulfide (reaction conditions hexane, 0-25 °C, 0.5-2 h).[34]... 

The formation of this complex may arise from sulfur insertion into the M-C bond of the corresponding thiocarboxamido complex (183). 

The formation of the thione complex 211 involves the coupling of two thioformaldehyde units, addition to the carbyne carbon of 210 to form a thiocarbene ligand, sulfur insertion into the metal-carbene bond, and... 

Synthesis via Sulfur Insertion into Metal-Carbon Bonds... 

A transamination reaction, using S-adenosylmethionine as the amine donor, gives 143. Urea formation, followed by sulfur insertion into the C-IH and the C-4H bonds gives biotin. 

The sulfur insertion into the C-6H bond occurs with inversion of stereochemistry [ 149]. Cysteine is the sulfur source [150]. Lipoic acid synthesis in a defined cell free system has not yet been accomplished. 

The biotin and lipoate synthases catalyze similar reactions, the insertion of sulfur into unactivated C—bonds to generate essential cofactors (Figures 8C and 8D). The substrate in the case of biotin synthase is dethiobiotin, with a single sulfur inserted into two C— FI bonds to generate the tetrahydrothiophene ring of biotin. In the case of lipoate synthase, two atoms of sulfur are inserted, one each into the C—bonds at positions 6 and 8 of octanoic acid to produce dihydrolipoate, which is typically isolated in the oxidized form shown in Figure 8D. (The actual... 

While [Zn(S2CNMe2)2] has been shown to be a better accelerator than other dithiocarbamate complexes (2002), its role has not been fully understood. Traditionally, it has been thought to involve the formation of a polythiocarba-mato intermediate, formed upon sulfur insertion into a zinc-sulfur bond, which in turn reacts with the rubber in a concerted fashion (Fig. 279). Over the past... 

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