Allyl mercaptoacetate

With this essential operation implemented, the crude Diels—Alder product (119) was then subjected to reaction with the lithium anion derived from allyl mercaptoacetate, an event that provided 120 in 53% overall yield from 117. Seeking next to create the maleic anhydride moiety, treatment of this product (120) with DBU in THF at ambient temperature then resulted in an intramolecular aldol reaction that furnished 121 in 93% yield as a single stereoisomer. Following decarboxylation at C-31 and dehydration of the alcohol group at C-11 to generate a thiobutenolide, a few... 

Real-Time FTIR. For our IR studies, we utilized a stoichiometrically equivalent amount of a trifunctional thiol, trimethylolpropane tris(2-mercaptoacetate), with a difunctional allyl, trimethylolpropane diallyl ether. The thiols were protected from oxidative polymerization by the addition of hydroquinone. The monomers and hydroquinone were purchased from Aldrich Chemicals and were used as received. This formulation was mixed for five minutes and then a commercial photoinitiator, Esacure TZT (Sartomer Inc.), which contained a blend of methyl benzophenones, was added at a level of 1.0% by weight of monomers to the formulation. Stirring was maintained for a further five minutes following the addition of the photoinitiator. The final formulation contained 2.0% by weight of hydroquinone. The samples were prepared prior to each experiment in order to ensure reproducibility of sample history. 

Thus, a semilogarithmic plot of the gel time as a function of 1/T should be linear, with the slope corresponding to the apparent activation energy. We have determined the gel times for a temperature range of 25°-50° C for a thiol-ene system consisting of stoichiometrically equivalent amounts of a trifunctional thiol, trimethylolpropane tris(2-mercaptoacetate), and a trifiinctional allyl monomer, triallyl isocyanurate. In this system, we also added 0.31% by weight of hydroquinone, to prevent premature polymerization, and 1.0% by weight of a commercial photoinitiator, Esacure TZT. 

Methyl (aUylthio)acetate, CH,—CHCH2SCH2COOCH3 (1). Mol. wt. 146,21. The reagent is prepared from allyl bromide and methyl mercaptoacetate (83% yield). 

MODEL STUDIES Early in this study it appeared that [2.2.1]bicyclic olefin resins added conventional crosslinking thiols in a rapid, exothermic, manner. These results appear to contradict earlier reports that internal olefins and cyclic olefins such as cyclohexene and cydopentene react only slowly with thiols. In reality, [2.2.1]bicydic olefins represent a separate dass of reactive olefins. These results are also consistent with reports (16-19) that bicyclic olefins such as norbomadiene are quite reactive to the addition of monofunctional thiols and thiyl radicals. In order to quantify the relative reactivity of norbornene resins with other "standard" ene components, a model study of the addition reaction was undertaken. A "typical" thiol (ethyl mercaptoacetate) was examined in a series of competitive reactions in which there was a defidency of olefin (Figure 4). Olefin substrates that were compared were norbornene, styrene, butyl vinyl ether, [2.2.2]bicydooctene and phenyl allyl ether. The results of that study are listed below in Table I. 

Most of the methods describing the preparation of Emtricitabine (and Racivir) rely on the construction of 1,3-oxathiolane ring by reaction of glycoMdehyde or glyoxalic acid derivatives with mercaptoacetic add or mercaptoacetic aldehyde (which exists as 1,4-ditiane 154). For example, one of the first of syntheses of this type commenced from allyl alcohol which was silylated and then subjected to ozon-olysis to give glycoMdehyde derivative 155 (Schane 36) [142], Reaction of 155 with mercaptoacetic add afforded 1,3-oxathiolane 156, which was reduced with LiAlH(OtBu)3 or DIBAL and then acetylated to form 157. Finally, reaction of 157 with silylated fluorocytosine derivative 158 followed by deprotection led to the formation of racemic 8 (Racivir). 

The reactions of isothiocyanates with a-mercaptoacetic acid continue to be the major method for the synthesis of rhodanines. A facile and uniform procedure for the large-scale preparation of some iV-alkyl-rhodanines has been reported, which involves allowing a primary amine RNH2 (R = Me, Et, allyl, or PhCHa) to react with carbon disulphide and ammonia, followed by treatment of the resulting ammonium alkyldithiocarbamate RNHC(S)S NH4+ with chloro-... 

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