Sulfur-Containing Carbonyl Derivatives

7 Sulfur-Containing Carbonyl Derivatives 13c Chemical Shifts (d in ppm) 

The chemical shifts of thiocarbonyl groups are higher by about 30 ppm than those of the corresponding carbonyl groups  

Carbonyl groups of thiocarboxylic acids and their esters are desUelded by about 20 ppm with respect to the corresponding oxygen compounds. 

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Chemical Shifts of Sulfur-Containing Carbonyl Derivatives... 

C Chemical Shifts in Sulfur Containing Carbonyl Derivatives (6 in ppm relative to TMS)... 

Active Raney nickel induces desulfurization of many sulfur-containing heterocycles thiazoles are fairly labile toward this ring cleavage agent. The reaction occurs apparently by two competing mechanisms (481) in the first, favored by alkaline conditions, ring fission occurs before desul-, furization, whereas in the second, favored by the use of neutral catalyst, the initial desulfurization is followed by fission of a C-N bond and formation of carbonyl derivatives by hydrolysis (Scheme 95). 

The fruit of pumpkin (Cucurbita pepo) is eaten boiled or baked. About 30 compounds have been identified in the volatile extracts of raw pumpkin, with the major classes of compounds being aliphatic alcohols and carbonyl compounds, furan derivatives and sulfur-containing compounds. Hexanal, ( )-2-hexenal, (Z)-3-hexen-l-ol and 2,3-butanedione have been identified as important for the flavour of freshly cooked pumpkins (Table 7.7) [35] however, studies using GC-O techniques are needed to get a better understanding of the character-impact compounds of pumpkins. 

Commonly utilized starting transition metal materials are oxides, halides, salts of fatty acids, complexes containing sulfur, etc. The role of the reducing agents is to lower the oxidation state of a metal and not to reduce the compound to an active metallic phase because this would, in most cases, lead to the inhibition of the reaction as shown by thermodynamic calculations. This point is also indicated by the formation of carbonyl derivatives possessing CO and other coordinating ligands as intermediates. 

Elemental sulfur and some organic sulfur compounds inhibit hydroformylation and hydrogenation catalyzed by cobalt carbonyls (1 2). In order to elucidate the mechanism of this "poisoning" effect, several new, sulfur-containing cobalt carbonyl derivatives have been prepared. 

The (cobalt carbonyl)-(carbon disulfide) complexes prepared in this laboratory by KLUMPP and coworkers (5, 6) belong apparently to a different class of sulfur-containing cobalt carbonyl derivatives. 

Numerous unusual organosulfiir transition metal compounds have been obtained by reactions of various metal carbonyls and cyclopentadienyl-metal carbonyls with certain mercaptans, sulfides, disulfides, and dithietenes (1,2). Other types of organosulfiir transition metal compounds have been obtained from metal sulfides and certain acetylene derivatives (3). This paper discusses a new and entirely different synthesis of new types of organosulfur derivatives of metal carbonyls with metal-sulfiir bonds. These new compounds have been obtained by thermal or photochemical decarbonylation of compounds of general formula CH S CH ) U(CO)yHC H )y (n = 1,2 or 3 M = Fe [x 2, y = 1], or Mn [x = 5, y = OJ) without metal-sulfur bonds. These sulfur-containing transition metal alkyl derivatives, none of which has been previously reported, may in turn be obtained from metal carbonyl anions and the chloroalkyl methyl sulfides CH S(CHpnCl. 

B1 SULFUR-CONTAINING COBALT CARBONYL DERIVATIVES,... 

Unwanted carbonyl compounds, which can produce an off-flavor in stored beer, are bound by sulfite derived from yeast metabolism. Yeast reduces the sulfate present in the wort to sulfite and sulfide, which is then consumed in the biosynthesis of sulfur-containing amino acids. If the growth of yeast comes to a standstill, excess sulfite is eliminated, increasing the stability of the beer to oxidative processes. 

The 3-methyl-2-butene-1-thiol is formed by recombination of a 3-methyl-2-butenyl radical and a thiol radical, possibly derived from sulfur-containing proteins present in beer. The alkenyl radical originates from photolysis of the acyloin group, which is composed of the tertiary alcohol function at C-4 and the carbonyl group of the 4-methyl-3-pentenoyl side chain at C-4 of the iso-alpha acids (Fig. 49). Alternatively,... 

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