Phenylthio group, replacement

Diphenylthioalkanes react with mercuric fluoride to give 1-fluoro-l-phenylthio-alkanes. Provide a detailed description of a likely mechanism for this reaction. Consider such questions as (1) Is an SnI or an Sn2 process most likely to be involved (2) Would NaF cause the same reaction to occur (3) Why is only one of the phenylthio groups replaced ... 

Phenylthiomethyllithium (2a) was used for the homologation of primary halides in a two-step sequence first halogen displacement by reagent (2a) or the organocuprate derivative (in the case of allylic compound) and then replacement of the phenylthio group by iodo by heating the sulfide with a large excess of methyl iodide in 1 M sodium iodide solution in DMF (Scheme 16). 

Coates et al. have extended this reaction to a method for gem-dialkylation at a methylene group adjacent to a carbonyl group. a-Phenyl thioketones can be alkylated at the carbon bearing sulfur, and the phenylthio group can be replaced by a second alkyl group by reduction-alkylation. For example, the ot-phenyl thio-ketone (1) is treated with sodium or potassium hydride in THF and then allowed... 

A 4-acetoxy substituent on a p-lactam is replaced by thio-acid salts in a zinc halide mediated reaction in non-protic medium (94TL3379) whereas copper salts and copper enolates are recommended for the replacement of a 4-phenylthio group (94TL5887). Intermolecular coupling reactions of 4-phenylseleno P-lactams are used to prepare tribactams (94CC441). 

However, by 1967 it was realized that thiabendazole was partly inactivated by metabolic hydroxylation in the 5-position, obviously a position which must be blocked. At about that time it was also found that anthelmintic action improved when a carbamato-group replaced the thiazoline ring in the 2-position. These discoveries led to a whole range of more active anthelmintics, namely mebendazole 6.37), and its variants in which the 5-benzoyl-group is replaced by a butyl (parbendazole), phenylthio (fenbendazole) or propylthio... 

The use of hydroxy-ester 5.231 as a template required its conversion to phenyl-thio amino derivative 5.232. This carbamate was converted to oxazolidinone 5.233. and replacement of the phenylthio group with allyl (see 5.234) was followed by ring opening to give 5.235. As in the two previous examples, the alkenyl moiety was converted to the acid via oxidative cleavage, giving 4R-(N-Boc-N-methyl-amino)-5S-methyl-3R-methoxyheptanoic acid, 5.236. ... 

An older route to (a-iodoalkyl)boronic esters involved preparation of pinacol (phenylthiomethyl)boronate (149), which could be deprotonated and die resulting anion alkylated by alkyl hahdes [80]. The phenylthio group can be replaced with iodo by treatment with methyl iodide and sodium iodide in acetonitrile. This route can only yield racemic (a-iodoalkyl)boronic esters, but it has been revived for preparation of... 

Two groups have independently developed a highly p-selective route to 2, 3 -didehydrodideoxy nucleosides, which involves the introduction of an a-phenylthio group at C-2 of the sugar unit to direct the orientation of the coupling in the desired sense 67,68 Scheme 5 illustrates the principle, and other workers have reported closely similar work n which selenium replaces sulphur. ... 

Sodium amalgam disodium hydrogen phosphate Replacement of sulfonyl groups by hydrogen with Zn/MeCOOH cf. 29, 792 with Na-amalgam in the presence of Na2HP04 as buffer, also replacement of phenylthio groups, s. B. H. Trost et al., Tetrah. Let. 1976, 3477... 

A stereospecific route to unsymmetrical olefins, always a useful procedure, involves sequential coupling of Grignard reagents (Ni,Pd catalysis) with 1-bromo-2-phenylthioethene. This room-temperature reaction involves first the replacement of bromine, followed by the phenylthio-group, to give the disubstituted alkene with very high selectivity and in good to excellent yields (Scheme 7), ... 

Photoirradiation of the (phenylthio)ethylenes (52a or 52b) in each case affords a low yield of a mixture of the normal product (53a or 53b, respectively) and the abnormal product (54a or 54b, respectively) together with products of higher molecular weight.97 No abnormal products are obtained when the 2-phenyl group of 52 is replaced by H or Me. Mechanisms have been proposed to account for these observations. 

DIB in combination with sodium azide and diphenyl disulphide or diphenyl diselenide can replace the methinic hydrogen of aliphatic, aromatic and heteroaromatic aldehydes by the phenylthio or phenylseleno group. The corresponding esters were obtained in moderate (for unsaturated aldehydes) to very good yields [109] ... 

In analogy with what has been observed for carbamates (described earlier), the trimethylsilyl substituent in, for example, 1-phenylthio-l-trimethylsilylalkanes is easily replaced by methoxy during anodic oxidation in MeOH [111,112]. Similarly, the anodic oxidation of a. a-bis(trimethylsilyl)xylenes in MeOH results in replacement of one trimethylsilyl group by methoxy [113]. 

If the 1,3-dithiane is replaced by a phenylsulfenyl or phenylsulfonyl group then the diastereoselectivity of the yeast reduction is slightly decreased. Nevertheless, useful chiral building blocks are prepared in this way. For example. l-phenylthio-2,3-butanedioneis reduced by baker s yeast to a mixture of fl /-(25,35)-l-phenylthio-2,3-butanediol and its. syw-isomer in a ratio of 86 14 in 66% yield. The anti-product is obtained in optically pure form by recrystallization from hexane/diethyl ether221. 

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