Sulfur analogs

Sulfides (RSR ) are the sulfur analogs of ethers Just as m the preceding chapter where we saw that the properties of thiols (RSH) are different from those of alcohols we will explore differences between sulfides and ethers m this chapter... 

Sulfides are sulfur analogs of ethers they contain the C—S—C func tional group They are named as al/cylthw derivatives of alkanes m sub stitutive lUPAC nomenclature The functional class lUPAC names of sul tides are derived m the same manner as those of ethers but the concluding word is sulfide... 

Sulfide (Section 16 1) A compound of the type RSR Sulfides are the sulfur analogs of ethers... 

The prefix thioxo- is used for naming =S in a thioketone. Sulfur analogs of acetals are named as alkylthio- or arylthio-. For example, CH3CH(SCH3)OCH3 is l-methoxy-l-(methylthio)ethane. Prefix forms for -carbothioic acids are hydroxy(thiocarbonyl)- when referring to the O-substituted acid and mercapto(carbonyl)- for the S-substituted acid. 

Benzene monoxide-oxepin and its sulfur analog are treated elsewhere (Chapter 5.1.7) (67AG(E)385). However, we point out here that electron-withdrawing substituents often favor the benzene oxide tautomer. The first study on oxides of the environmentally hazardous polychloro- and polybromo-biphenyls shows that they exist mainly in the benzene oxide form (81JOC3721). Oxides of polynuclear aromatic hydrocarbons (PAH) also exist mainly in the fused-ring oxirane form. 

There are, however, some crown type compounds which contain no structural feature except the thiophene subunit, and these deserve some comment here. This is especially true since one of these compounds was prepared very early in the history of crown compounds. Ahmed and Meth-Cohn were interested in sulfur analogs of the porphyrin ring system and prepared compound 7 in 1969 by the method shown in Eq. 

The facile a,a diacylation with arylisocyanates has been applied to the synthesis of polymers (434-436), while the monoacylation products have been used as intermediates for the synthesis of substituted a-quinolones and their sulfur analogs (437). 

The reactions of (174) with various amines has been studied." " Hydrolysis of the hexamine salt of (174) gave not the symmetric diamine but (184) via a cyclic intermediate. The pyrolysis of 5-methyl-2-thenyltrimethyl ammonium hydroxide (185) is claimed to give (186) through a 1,6 Hofmann elimination reaction. The Bischler-Napieralski cyclization has been applied to acetyl derivatives of 2-(2-thienyl) ethylamine and 2-(3-thienyl) ethylamine for the preparation of sulfur analogs of isoquinoline. ... 

With X = RN the C-1 electrophilic center is most active, and five-membered heterocycles 131 are generated (69ZOR1179). With X = O there is a competition between C-1 and C-3 electrophilic centers, the role of the latter increasing on going to sulfur analogs (X = S) in accord with a decrease in the - -M effect in this series (81UK1252). 

Thiophene is the sulfur analog of pyrrole. The sulfur atom is sp2-hybridized and lias a lone pair of electrons in a p orbital perpendicular to the plane of the ring. Sulfur also has a second lone pair of electrons in the ring plane. 

Compounds with a smaller/C., and larger pKa are less acidic, whereas compounds with a larger/Ca and smaller plsimple alcohols like methanol and ethanol are about as acidic as water but substituent groups can have a significant effect, tert-Butyl alcohol is a weaker acid, for instance, and 2,2,2-trifluoroethanol is stronger. Phenols and thiols, the sulfur analogs of alcohols, are substantially more acidic than water. 

Thiols (R—S—H) and sulfides (R—S—R ) are sulfur analogs of alcohols and ethers, respectively. Both functional groups are found in various biomolecules, although not as commonly as their oxygen-containing relatives. 

Thiols, sometimes called mercaptcms, are sulfur analogs of alcohols. They are named by the same system used for alcohols, with the suffix -thiol used in place of -ol. The -SH group itself is referred to as a rnercapto group. 

Sulfides are the sulfur analogs of ethers just as thiols are the sulfur analogs of alcohols. Sulfides are named by following the same rules used for ethers, with sulfide used in place of ether for simple compounds and alkylthio used in place of alkoxy for more complex substances. 

Thiols, the sulfur analogs of alcohols, are usually prepared by Sjv 2 reaction of an alkyl halide with thiourea. Mild oxidation of a thiol yields a disulfide, and mild reduction of a disulfide gives back the thiol. Sulfides, the sulfur analogs of ethers, are prepared by an Sk2 reaction between a thiolate anion and a primary or secondary alkyl halide. Sulfides are much more nucleophilic than ethers and can be oxidized to sulfoxides and to sulfones. Sulfides can also be alkylated by reaction with a primary alkyl halide to yield sulfonium ions. 

The sulfur analog, 5//-dibenzo[d,./][1,3]diazcpin-6(7//)-thiotie (14), is formed from biphenyl-2, 2 -diamine and carbon disulfide.175... 

The use of the disulfide (13), which can dissociate thermally to give a sulfur analog of TEMPO (Section 9.3.6.1), has also been explored for controlling S polymerization though poor results were obtained.40... 

Alkanesulfonates are the petrochemically derived sulfur analogs of soaps, which are alkane carboxylates based on renewable resources. The main difference between alkanesulfonates and soaps is, however, that alkanesulfonates consist of a rather complex mixture of homologs with different carbon chain lengths and isomers with an almost statistical distribution of the functional group along the hydrophobic carbon chain (Fig. 1), whereas soap is a mixture of homologs of alkane 1-carboxylates with an even number of carbon atoms. 

The sulfur analog of hydrogen peroxide also exists and is an example of a polysulfane, a catenated molecular compound of composition HS—S —SH, where n can take on values from 0 through 6. The polysulfide ions obtained from the polysulfanes include two ions found in lapis lazuli (Fig. 15.15). 

Thiols and sulfides are occasionally prepared by treatment of Grignard reagents with sulfur.Analogous reactions are known for selenium and tellurium compounds. 

Hydration of compounds 2, 3, 4, 5 was found to be first order both in substrate and in hydronium ion (4-10). Furthermore, a careful kinetic study of compounds 2c-g and the sulfur analog 4 revealed that the hydration rate at constant ionic strength was dependent on the buffer concentration and hence was general acid catalyzed. 

Yu, Q.S. Lu, B.Y (1994) Total Synthesis of Racemic Physostigmine, Physovenine and its Sulfur Analog by the Oxindole-5-O-tetrahydropyranyl Ether Route. Heterocycles, 39, 519-525. 

The simplest sulfur analogs of tetrahedral intermediates are the sulfuranes... 

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