Trithianes, formation

This name applies to formation of 5. Names for formation of 6,7, and 8, are, respectively, thioxo-de-oxo-bisubstitution, dimercapto-de-oxo-bisubstitution, and carbonyl-trithiane transformation. 

Poly(thioformaldehyde) can also be obtained by reaction of hydrogen sulfide with formaldehyde in acid media (8). Again the key intermediate is 1-hydroxy-2-oxa-4,6-dithioheptane-7-thiol. Though acid conditions favor formation of trithiane, use of a high CH20/H2S04 ratio results only in polymer formation. Credali and Russo (8) believe this to be a topochemical reaction between the dithioheptane and mercaptomethanol. 

Wilson, el al. (41) also confirmed the presence of polysulfur heterocyclics in meat including thialdine (5,6-dihydro-2,4,6-tri-methyl-l,3,5-dithiazine) and trithioacetone (2,2,4,4,6,6-hexame-thyl-1,3,5-trithiane). Wilson (42) later discussed the possible routes of formation of some of these compounds from cysteine. Thialdine was found by Brinkman, et el. (43) in the headspace volatiles of beef broth. These workers also identified 3,5-di-methyl-1,2,4 - trithiolane from the same source. Both cis and trans isomers of this compound had previously been identified as flavor components of boiled beef by Chang, jit aL. (44) and Herz (45). 

The formation of 5,6-dihydro-2,4,6-trimethyl-l,3,5-dithiazine, 2,4,6-trimethyl-1,3,5-trithiane, and 3,5-d ime thy1-1,2,4-trithiolane by heating of acetaldehyde, hydrogen sulfide, and ammonia was outlined by Takken and coworkers (36) and is summarized in Figure 4. Under oxidative conditions, dialkyltrithiolanes are formed at low pH there is conversion to trialkyltrithianes at elevated temperature isomerization into trisulfides occurs, which compounds disproportionate into di and tetrasulfides and in the presence of ammonia, dithiazines are formed. These compounds and the conditions for their formation are of extreme importance for the production of desirable meat flavors. 

Polysulfide Heterocycllcs. Polysulfur heterocyclics, including thialdine (5,6-dihydro-2,4,5-trimethyl-1,3,5- dithiazine) and trithioacetone (2,2,4,4,6,6-hexamethyl-l,3,5-trithiane), have been identified in meat flavor extracts (41). The formation of these compounds is shown in Figure 4. 

Aliphatic sulfides can be efficient co-initiators for the photoinduced polymerization induced by benzophenone [185, 186]. An exceptionally strong effect was observed for 2,4,6-trimethyl-1,3,5-trithiane (TMT). A model reaction for free-radical formation during photoreduction of an initiator triplet state by a sulfide is the photoreduction of benzophenone by dimethyl sulfide [171, 187-189]. In this process it was established that electron transfer from the sulfur atom to the triplet state of the benzophenone is a primary photochemical step. In this step, radical ions are formed. The overall quantum yields of photoproducts (ketyl radicals and radical anions) are low (Ed) 0.26) in aqueous solution, in the range 0.16-0.20 in mixed water-acetonitrile solution and less then 0.01 in pure acetonitrile. These results suggest that, in organic solvents, back electron transfer within the radical-ion pair to regenerate the reactants is the dominant process. 

This reaction scheme can explain, for example, the formation of 1,3,5-trithiane, which is one of the main components in the pyrolysis products of polythiomethylene. In a similar reaction, polythioethylene generates 1,4-dithiane, but the formation of cyclic fragments from poly(3-vinylthiobenzene-1-thiol) is less favored and the decomposition occurs mainly as indicated below ... 

C—C Bond formation. s-Trithiane has been used very much like 1,3-dithiane (2, 182-187) in organic synthesis 2-3 hojvever, the carbanion derived from this reagent tends to undergo carbenoid decomposition. Metalated trithiane reacts readily with primary halides to give 2-alkyl-s-trithianes convertible into aldehydes, as shown for a preparation of n-pentadecanal 1... 

Table 12 Spectral characteristics, formation oonstants (Kcj), and enthalpy changes (AH) for CT complexes of 1,3,5-trithiane with various eiectron acceptors at 25 °C and the ionization potentials of these donors <1994BCJ2006>...

Starting from 1,3,5-trithiane, three novel mono- to trifulvathianes 163-165 have been prepared by (1) formation of the 1,3,5-trithiane anion and (2) reaction with either 4,5-dimethyl-l,3-dithia-2-iminium cation 166a or the 4,5-dimethyl-l,3-dithia-2-methylthiolium cation 166b (Figure 9). Spontaneous loss of amine or mercaptan provides... 

The role of the isomers of 2,4,6-trimethyl-l,3,5-trithiane as co-initiators in benzophenone-induced photopolymerizations was pursued by studying the primary photochemical reactions by nanosecond laser-flash photolysis <2001JPH133> it was found that the polymerization efficiency of the co-initiator did not follow the efficiency of photo induced formation of the initiating radicals however, detailed mechanisms of the various stages of polymerization were proposed <1998JPH21, 1999MM2173, 2001JPH133>. 

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