Thiol chloroformates

Thiolactic acid Thiol chloroformates Thiolene polymers Thiols... 

A hydrogen-bond acidity scale has been constructed by Frange and coworkers and by Sraidi based on log K values for complexation with pyridine N-oxide in cyclohexane (equations 22 and 23). Values for phenols and, for comparison, thiols, chloroform, pyrrole and alcohols are collected in Table 5. There is a fair measure of agreement between log K and log Kf n = 16, r = 0.992) and log (n=9,r = 0.972). 

Cross Coupling of (a-(Acyloxy)alkyl)tributylstannanes with Thiol Chloroformate... 

Falck and co-workers report cross-coupling of (a-(acyloxy)alkyl)tributylstan-nanes with thiol chloroformate using a catalytic amount of copper salts. For example, (a-(acetyloxy)benzyl)tributylstannane 13 was treated with thiol chloroformate 14 in the presence of 8 mol% of CuCN in toluene at 75 °C for 21 h to give the thiol ester 15 with 98% yield (Eq. 14) [21]. 

Aliphatic Alcohols and Thiols. Ahphatic alcohols on reaction with chloroformates give carbonates and hydrogen chloride. Frequendy, the reaction proceeds at room temperature without a catalyst or hydrogen chloride acceptor. However, faster reactions and better yields are obtained in the presence of alkaU metals or their hydroxides, or tertiary amines. Reactions of chloroformates with thiols yield monothiolocarbonates (14). 

Trimethylsilyl trichloroacetate, K2CO3, 18-crown-6, 100-150°, 1-2 h, 80-90% yield.This reagent silylates phenols, thiols, carboxylic acids, acetylenes, urethanes, and /3-keto esters, producing CO2 and chloroform as byproducts. 

The Hoc group was developed for tryptophan protection to minimize alkylation during BOC-mediated peptide synthesis. It is introduced with the chloroformate (NaOH, CH2CI2, Bu4N HS04 ) and can be cleaved with HF without the need to include thiols in the cleavage mixture. 

The solid disulfide reacts explosively with chlorine or bromine. At low temperatures in certain non-aqueous solvents, e.g. chloroform, CISCSN3 and BrSCSN3 are probably formed, but the extreme instability of these compounds has precluded their exact analysis and description. However, the reaction between cyanogen bromide and the potassium salt of the thiol yields the well-defined cyanide NCSCSN3,... 

Mono-substitution occurs most readily in the stepwise replacement of the halogen substituents of 2,4,6-trichloro-s-triazine with aqueous methanol and sodium bicarbonate (30°, 30 min), the monomethoxy derivative (324) is obtained on heating (65°, 30 min), the disubstitu-ted derivative is formed and on brief heating (65°) with the more basic sodium carbonate or methanolic sodium hydroxide (25°, 3 hr) complete methoxylation (320) occurs. Ethanolic ethoxide (25°, 1 hr) or sodium carbonate (35°) is sufficient to give complete ethoxy-dechlorination. The corresponding phenoxy derivatives are obtained on treatment with one (0°), two (15°, 1 hr), or three equivalents (25-70°, 3 hr) of various sodium phenoxides in aqueous acetone. The stepwise reaction with phenols, alcohols, or thiols proceeds in better yield in organic solvents (acetone or chloroform) with collidine or 2,6-lutidine as acid acceptors than in aqueous sodium bicarbonate. ... 

Chloroformates or carbonyl chloride react with 2-piperidone hydrazones to give triazolopyridine-3-ones (86JAP(K)69776), and there are further examples of the production of 3-thiols from a hydrazine and carbon disulfide (83USP4419516, 88EUP254623). 

Hydrazines of type 89 react with various carbonic acid derivatives to furnish cyclized product. Under basic conditions (KOH), in the presence of carbon disulfide or arylisothiocyanates, the cyclized thione 90 is obtained (Scheme 7) <1966JOG3528, 1984JCCS315>. Analogous reactions performed in the absence of base gave 91 as a 3-thiol when performed with carbon disulfide, as a 3-hydroxyl with methyl chloroformate, or as a 3-arylamino with arylisothiocyanates in the presence of dicyclohexylcarbodiimide (Scheme 7) <1986JHC1339, 1992IJB467>. 

An alternative formulation of the phase-transfer DCC concept was reported in 2008 by the Sanders group [75]. In this case, thiol monomers were dissolved in water on either side of a U-tube containing chloroform (Fig. 1.23). After allowing the system to reach equilibrium, monomer distribution was identical in both aqueous solutions, and mixed species (e.g., 51) were observed in the chloroform layer. 

Like its monomeric counterpart, the polymeric reagent is inert to simple amines, amides, alcohols and phenols, but easily oxidizes thiols to disulphides, phosphines to phosphine oxides, hydroquinone and catechol to quinones, and thioketones, thioesters and trithiocar-bonates to the corresponding 0x0 derivatives, in dichloromethane, chloroform or acetic... 

Adsorption of a specific probe molecule on a catalyst induces changes in the vibrational spectra of surface groups and the adsorbed molecules used to characterize the nature and strength of the basic sites. The analysis of IR spectra of surface species formed by adsorption of probe molecules (e.g., CO, CO2, SO2, pyrrole, chloroform, acetonitrile, alcohols, thiols, boric acid trimethyl ether, acetylenes, ammonia, and pyridine) was reviewed critically by Lavalley (50), who concluded that there is no universally suitable probe molecule for the characterization of basic sites. This limitation results because most of the probe molecules interact with surface sites to form strongly bound complexes, which can cause irreversible changes of the surface. In this section, we review work with some of the probe molecules that are commonly used for characterizing alkaline earth metal oxides. 

The greater transfer constant for carbon tetrabromide compared to the tetrachloride is due to the weaker C— Br bond. The low Cs value for chloroform compared to carbon tetrachloride is explained by C—H bond breakage in the former. The thiols have the largest transfer constants of any known compounds due to the weak S—H bond. 

The immersion of a polycrystalline gold electrode into a chloroform/methanol (2 1, v/v) solution of the tetrachloride salt of 6 (Fig. 7.4) results in the adsorption of this electroactive thiol on the metal surface.270 Consistently, the cyclic voltammogram (Fig. 7.5a), recorded after an immersion time of 24 h and extensive rinsing of the electrode surface, shows the reversible reduction of the bipyridinium dications to the corresponding radical cations. In addition, zp increases linearly with v (Fig. 7.6a),... 

The liquid has strong smell of thiol and undergoes aerial oxidation at room temperature. It should be handled under dry dinitrogen or argon. 1H NMR (chloroform-d) 8 2.5-2.9(mult), 2.12 (s), 1.04 (s). 

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