Sodium methyl thiolate

Knochel and co-workers have carried out a series of nucleophilic substitution reacion on ( )-allyl bromide using thiolate ions. The reaction between bromide 326 and lithium phenylthiolate yielded the ( )-sulfide 327 exclusively. However, treatment of ( )-sulfide 327 with the more nucleophilic reagent sodium methyl thiolate led to a 20 80 mixture of 327 and ( )-methyl sulfide 328. They proposed that either a S- 2 mechanism is operative, or two S- 2 substitutions eventually resulted in the thermodynamically more stable sulfide (ii)-methyl sulfide 328. A similar reaction of 326 with aniline in excess or its chloromagnesium amide gave a mixture of 5 n2 and 5 n2 products 329 and 330 which slowly equilibrate to give S-f 2 product 329 in 78% yield (Scheme 3.143). 

Isocolchicine (33) (only ring C is shown in Fig. 12), when reacted with sodium methane thiolate in aqueous methanol, was reported to give two reaction products, with the isothiocolchicine structure 34 assigned to the minor one (55). It has been shown on the basis of a detailed H-NMR analysis that the major reaction product is the pseudothiocolchicine (35) (56). Addition of the methyl sulfide occurred on either side of the carbonyl group. Both compounds, 34 and 35 shown in Fig. 12, afforded on reduction with Raney nickel the same isocolchicide (36). 

Compound 136 gave the addition elimination products 142 with methyl thiolate (R = Me, 68%) or mercaptans (R = alkyl, aryl and heteroaryl, 31-88%) in CH2CI2/DME The use of sodium thiolate in MeOH afforded 143, which was alkylated at a sulfur atom to give 142 (R = Bn 79% yield, R = farnesyl 47% yield) using alkyl bromides and a base. 

It should be noted, however, that although some heteronucleophiles such as amines and thiolates underwent clean nucleophilic substitution, treatment with sodium methylate produced enolether 248 as the major product [103]. Owing to electronic polarization, acceptor-substituted allenes should be ideal candidates for regioselective additions. Nevertheless, ketone 251 demonstrates that again the choice of the catalyst is crucial for a clean directed addition. Moreover, cycHzation reactions may make things quite complicated [104]. 

Thioetherification of PECH is feasibly performed in DA-solvents as already described in the patent (20J. For example, the highest substitution was obtained by the reaction of P(ECH-EO)(1 1 copolymer of epichloro-hydrin and ethylene oxide) and equimolar thiophenoxide in HMPA at 100°C for 10 h as DS 83% for sodium and 93% for potassium salts. The DS in our nucleophilic substitution was estimated by the elemental analysis as well as the titration of liberated chloride ion with mercuric nitrate (21). In the latter method, reacted medium was pretreated with hydrogen peroxide when the reductive nucleophiles which can react with mercuric ion were used. As described before for PVC, thiolation was also achieved conveniently with iso-thiuronium salt followed by alkaline hydrolysis without the direct use of ill-smelling thiolate. The thiolated PECH obtained are rubbery solids, soluble in toluene, methylene chloride, ethyl methyl ketone and DMF and insoluble in water, acetone, dioxane and methanol. 

The ethyl ester of l-cyclopropyl-7-(2,6-dimethyl-4-pyridyl)-5,6,8-trifluoro-4-oxo-1,4-di-hydroquinoline-3-carboxylic acid26 and of the closely related (7>)-10-(2,6-dimethyl-4-pyridyl)-8,9-difluoro-3-methyl-7-oxo-2.3-dihydro-7//-pyrido[1,2,3-tfe]-l,4-bcnzoxazine-6-carboxylic acid 427 can be thiolated in tetrahydrofuran at low temperature, using the strong base sodium hydride. 

The resistance of the furoxan ring to chemical attack allows derivatives to be prepared via the reactions of the substituents (Section 4.22.3.4). Carboxylic acids are available by permanganate oxidation of methyl derivatives or by hydrolysis of the corresponding esters reaction with ammonia affords carboxamides. Acylfuroxans provide a source of hydroxyalkyl compounds by reduction, and oximes, for example, via nucleophilic addition. Acylation and oxidation of aminofuroxans allows the amide and nitro derivatives to be prepared. Nucleophilic displacements of nitro substituents can take place, but can be somewhat hazardous on account of the explosive nature of these compounds. Alkoxy derivatives are formed with sodium alkoxide, while reaction with thiolate anions yields sulfides, from which sulfones can be synthesized by peracid oxidation. Nitrofuroxans have also been reduced to... 

Several thiols occur naturally for example, skunk secretion contains 3-methyll-butanethiol and cut onions evolve 1-propanethiol, and the thiol group of the natural amino acid cysteine plays a vital role in the biochemistry of proteins and enzymes (see Introduction, p. 2). Primary and secondary thiols may be prepared from alkyl halides (RX) by reaction with excess sodium thiolate (SN2 nucleophilic substitution by HST) or via the Grignard reagent and reaction with sulfur. Tertiary thiols can be obtained in good yields by addition of hydrogen sulfide to a suitable alkene. Thiols can also be prepared by reduction of sulfonyl chlorides (Scheme l).la,2a... 

The introduction of steric constraints in these ligands can enforce meridional coordination of the three central donors and trara-coordination of the terminal thiolate donors. The use of ligands with pyrimidinyl substituents such as (54), a neutral S2N5-donor obtained in situ from 2,6-bis(chloro-methyl)pyridine and sodium pyrimidine-2-thiolate in dmf, opens the way for the synthesis of coordination polymers.70... 

Noteworthy is the reaction of methyl 4-bromobut-2-enoate with 5< c-butyl or ferf-butyl thiolate, which only gave the cyclopropanecarboxylate when the reaction was carried out in nonpolar solvents and with lithium as the counterion. In this case the lithium cation is coordinated with both the sulfur atom and the carbonyl oxygen atom as shown in 1. When this ability of coordination diminishes, cyclopropanes are not formed. Thus, by using sodium or potassium as counterion or by using chelating solvents, e.g. dimethylformamide, the yields drop dramatically (cf. Table 20, entries 1 - 5). 

Vinyl bromides react with copper(i) thiolates, both aliphatic and aromatic, to give vinyl sulphides. Vinyl bromides studied include ]8-bromostyrene and l-bromo-2-methyl-l-propene. This method of synthesis of thioethers is claimed to be superior to that using sodium thiolates and most other reported methods . 1,2-Dibromoethylene gives a mixture of cis (18%) and Irons (42%) 1,2-diphenylthioethylene with copper(i) benzene-thiolate, but with copper(i) ethanethiolate ethylthioacetylene is formed with the elimination of hy ogen bromide , ... 

The thiolate is generated in situ from sodium hydride and the corresponding thioF. Aryl methyl ethers with strong electron-withdrawing substituents (G) require milder conditions for cleaving the ether linkage, but these compounds are also likely to suffer substitution of the aromatic carbon with strong carbon nucleophiles. ... 

Cellulosic membranes are developed as a novel dmg delivery system, which is expressed to use on the skin and used as a mucus membrane of stomach, ear, nose, eye, rectum, and vagina. The goal excipients of these preparations are adhesive and film-former polymers. Modified cellulose, especially cellulose ethers, are extensively applied in bio-adhesives such as nasal, vaginal, ocular, buccal, and transdermal inventions only or by blend with additional polymers. Further newly applied ethers of cellulose in bio-adhesives contain anionic ether derivatives such as sodium carboxy-methyl cellulose (NaCMC) and non-ionic cellulose ethers such as hydoxypropyl cellulose (HPC), carboxymethyl cellulose (CMC), hydroxyethyl cellulose, ethyl cellulose (EC), hydroxylpropylmethyl cellulose (HPMC), or methyl cellulose (MC). Capability of polymer to absorb water from mucus and pH of objective area are main features defining the adhesive power of polymers. One benefit of cellulose ethers, such as HPC and NaCMC, is smaller dependence of adhesion period and their adhesion strength to pH of medium than thiolated bio-adhesive polymers and polyacrylate... 

Zakharkin and co-workers have studied, in detail, the synthesis and reactions of fluorovinyl-substituted carbaboranes (Vol. 1, p. 89). In Scheme 12 are shown some of the reactions described. Apparently the ability of the o-carbaboranyl nucleus to stabilize a negative charge during nucleophilic addition-elimination reactions exceeds that of either chlorine or trifluoro-methyl, attack on the double bond occurring p to the nucleus. > 4,4-Dichloro-3,3-difluoro-l-phenylcyclobutene reacts with aryl-lithium compounds, sodium thiolates NaSAr (Ar = Ph,p-MeC,H4,orn-H2N-CeH4), or pyridine or other heterocyclic bases by substitution with rearrangement. 

Preparation. Sodium diisopropylphosphonate generates 5-methyl diisopropoxyphosphinyldithioformate when treated with carbon disulfide and methyl iodide. The reduction of this compound with sodium borohydride followed by trapping of the thiolate with methyl iodide leads to diisopropyl methylsulfanyl-methylphosphonate(eq 1). ... 

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