From thiono esters

Radicals formed by fragmentation of xanthate and related thiono esters can also be trapped by reactive alkenes.217 The mechanism of radical generation from thiono esters was discussed in connection with the Barton deoxygenation method in Section 5.4. 

Thiazoles from Ethyl Isocyanoacetate and Thiono Esters Ethyl Thiazole-... 

THIAZOLES FROM ETHYL ISOCYANOACETATE AND THIONO ESTERS ETHYL THIAZOLE-4-CARBOXYLATE... 

BC13 convert 0=0 groups of ketones, lactones, and lactams to G=S groups119 and H2S-Me3SiCl-i-Pr2NLi converts carboxylic esters to thiono esters.120 Carboxylic acids RCOOH can be converted directly to dithiocarboxylic esters RCSSR, 120a in moderate yield, with P4S, and a primary alcohol R OH.121 Thioketones can also be prepared by treatment of ketones with P4SI0,122 and from oximes or various types of hydrazone (overall conversion C=N------> C=S).123... 

Only very few among the common amino acids possess a pK within the range 5.8-7.0. Therefore, the imidazole ring of histidine was suspected very early to represent the group responsible for nucleophilic attack on the substrate (38). The pK of free imidazol is 6.9 (39) that of imidazol, contained in histidine or its peptides, varies between 5.6 and 7.1 (40). Imidazol is well known to form unstable acyl derivatives, which undergo spontaneous hydrolysis because of the presence of the resonating triad unit —-N—C= N— (41). In addition, imidazol and its derivatives catalyze the hydrolysis of certain esters, especially those derived from phenols (42). Likewise, the behavior of imidazol towards thio esters reflects exactly the specificity of ChE s (see IV, 4). Thus, thiol esters are split (43), whereas thiono esters are resistant (21). 

Thiono esters RCSOR can be reduced to ethers RCH2OR with Raney nickel (14-27). " Reaction of thio esters, such as C—0C(=0)Ph with Ph2SiH2 and Ph3SnH with BEt3, followed by AIBN (p. 935) leads to reduction of the C=S unit to give an ether. " " Since the thiono esters can be prepared from carboxylic... 

Equation (24) has been chosen as an example of the radical deoxygenation of secondary alcohols via thiono esters [58], whereas Eq. (25) represents an example of deamination of primary amines via isocyanides [7, 54]. The reaction mechanism of these reductions is similar to that described for tin hydride, i.e. attack of silyl radical on the C=S or N=C moieties to form a radical intermediate which undergoes -scission to form alkyl radicals. Hydrogen abstraction from the hydride gives the product and the (TMS)3Si radical, thus completing the cycle of this chain reaction. 

Another type of ylide (254), resonance-stabilized by a thiono-ester group, has been presented recently as the product from the reaction of... 

JR has found application in endothiopeptide synthesis. One carbonyl group of a cyclohexapeptide is selectively thionated with JR (eq 7). The cyclic thiopeptide exhibits enhanced effectiveness as an inhibitor of triosephosphate isomerase (TIM). This results from the pronounced alteration of the backbone conformation which is due to different hydrogen bridges. Belleau s reagent, BR, can be used similarly to JR to prepare thiooligopep-tides selectively or thiono esters of the carbohydrate series (eq 8). ... 

Synthesis of Derivatives of Thionocarboxylic Acids.—Thiono-esters are obtained by the reaction of dialkoxycarbonium ions with NajS or anhydrous NaHS in acetonitrile (Scheme 6). Cyclic carbonium salts from 1,2- or 1,3-diols give monothiono-esters of these diols. The tetrahedral intermediates in this process may be alkylated to give... 

Without additional reagents Sdionberg rearrangement Thiol- from thiono-carbamic acid esters Newman-Kwart-rearrangement, s. 22, 625 Korte, B. 106, 2419 (1973) WM.r. NCSOR NCOSR s. a. H.-J. Kurth, U. Kraatz, and F. 

The thioacylating properties of (169) have already been mentioned, and thiono-esters are formed from it by reaction with alkoxides. Thioacylation of methoxide ion can also be achieved by R C(S)SSR , which is obtained from R CS2 R2NHa+ and R SC1. Dithiocarboxylates may be prepared in an analogous manner from mercaptides. ... 

Deoxygenation of primary and secondary alcohols.1 This deoxygenation has been effected by reduction of the thiocarbonyl esters with tributyltin hydride and AIBN as the radial initiator (11, 550). A newer, milder method uses diphenylsilane in a radical chain reaction initiated by triethylborane and air. Even secondary thiono-carbonates, particularly those derived from 4-fluorophenol, are deoxygenated at 25°. 

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