Phenyl thioethers

Although a sulfhydryl group generally is not converted to an S-phenyl thioether, thiophenol can be used to introduce sulfur into molecules, and thus the phenyl group serves as a suitable protective group that can be removed by electrolysis (-2.7 V, DMF, R4N+X ). ... 

K2CO3 or CS2CO3, DMF or CH3CN, PhSH, 88-96% yield. This process is not always selective for p-nosylate cleavage. Some amines, especially cyclic ones, tend to form 4-phenyl thioethers by nitro displacement as by-products of the cleavage process. This seems to be true only for the p-nosylate. ... 

N-allyl-2,4-dinitroaniline, catalysis of nucleophilic substitution by, 422 N-allyl-l-naphthylamine,rearrangement of,473 allyl phenyl thioether, rearrangement of, 473, 474... 

As the final example in this section, a Li-mediated carboaddition/carbocycliza-tion process will be described. Thus, Cohen and coworkers observed a 5-e%o-trig-cy-clization by reaction of the lithium compound 2-349 and a-methyl styrene 2-350 to give 2-352 via 2-351 (Scheme 2.82). Quenching of 2-352 with methanol then led to the final product 2-353 [189]. In this process, 2-349 is obtained by a reductive lithia-tion of the corresponding phenyl thioether 2-348 with the radical anion lithium 1-(dimethylamino)naphthalenide (LDMAN) (2-354). Instead of the homoallylic substance 2-348, bishomoallylthioesters can also be used to provide substituted six-membered ring compounds. 

Cohen and coworkers also used a metallo-ene reaction starting from allylic phenyl thioethers such as 4-337 (Scheme 4.75) [116]. With tBuOK/nBuli, 4-338 is... 

Treated with ZnBr2 followed by enamines, phenyl thioethers 829 derived from aryl aldehydes are converted to (l-(phenylthio)alkyl ketones or aldehydes 830 in moderate to good yields (Equation 19). Enamines used in these syntheses are (1) morpholine enamine derived from diethyl ketone, (2) diethylamine enamine of propiophenone, (3) piperidine enamine derived from isovaleraldehyde, and (4) pyrrolidine enamine of cyclohexanone <2000H(53)331>. 

Cutting and Parsons described the transformation of acetylenic alcohols 314 into allenyl phenyl thioethers 316 by a two-step procedure (Scheme 8.85) [174], Deprotonation of alkynes 314 with n-butyllithium is followed by addition of phenylsulfenyl chloride, forming sulfenyloxy intermediates which subsequently rearrange to allenic sulfoxides 315. Treatment of allenes 315 with methyllithium results in loss of the sulfoxide moiety to form allenyl sulfides 316 in reasonable yields. 

The reaction of the thiolated PVC with Chloramine T carried out and the structure ( ) of the resultant polymer was examined (1 ). In the case of phenyl-thioether, the sulfilimine structure (2) was mainly produced accompanied with, in part, the sulfenamide structure (8,) binded to the main chain with N atom, the case of allyl thioether derivative containing C=C moiety in the pendent group, the sulfilimine (9) formed rearranged exclusively in Claisen type to the sulfenamide structure (10) connected to the main chain with S atom. 

Irradiation of 5-phenyl thiolacetate (203) in benzene gives diphenyl disulfide (206) as major product (52%). However, minor amounts of ortho-rearranged (204) and para-rearranged (205) products are also formed, along with thiophenol (17%) and methyl phenyl thioether (208) (19%) (Scheme 54) [155],... 

Dialkoxymethyllithium compounds, for example 2-lithio-l,3-dioxan (311), are generated in situ as shown in equation 69, either by reductive lithiation of a phenyl thioether with a lithium arene or by transmetallation of the corresponding trialkylstannyl compound. Subsequent quenching with electrophiles leads to the usual alkylated or functionalized species ... 

Although the most important reaction of rednctive carbon-snlfnr bond cleavage involves alkyl phenyl thioethers, arene-catalyzed lithiation has also been studied using other snlfnr-containing componnds, snch as thiols, disnlhdes, snlfoxides and sulfones. 

The same protocol shown in Scheme 123 was used with cyclopropyl phenyl thioether, so cyclopropylic 1,3-diols 444 were obtained in 31-53% yield °. ... 

His group [312,313] has done important work on the reductive cleavage of the C-S bonds of phenyl thioethers. These workers have shown the potential of two radical anions lithium p,p -di-t-butylbiphenylide (LDBB) and lithium l-(dimethylamino)naphthalenide (LDMAN) as reducing species. 

Cyanomethyldimethylsulfonium -toluenesu1fonate, AT79 Cyanomethyl phenyl sulfide, AMUl Cyanomethyl phenyl thioether,... 

Ethyl 3 phenylpropenoate, AT50 Ethyl phenylpropiolate, AT22 Ethyl phenylpropynoate, AT22 Ethyl phenyl sulfide, ANY3 Ethyl phenyl thioether, AN73... 

Homofamesyl iodide 7 was prepared by the reaction sequence shown in the margin. Of interest here is the two-step transformation of an alkyl halide into a Crextended alkyl halide.9 Compound 30 is first subjected to a nucleophilic substitution by an urganolithium species with formation of a homoallylic phenyl thioether This is then methylated in a second step to an intermediate sulfonium salt. The final SN2 reaction with an iodide ion releases thioanisol as a stable leaving group to give compound 7. 

Thiol B.P. °C (/mmHg) M.P. °C 2,4- Dinitro- phenyl- thioether °C 2,4- Dinitro- phenyl- sulphone °C 3,5- Dinitro- thio- benzoate °C Hydrogen 3-nitro- thio- phthalate... 

Methylidenation of allylic thioethers. Methylidenation of an allylic phenyl-thioether with methylene iodide-diethylzinc is accompanied by a 2,3-sigmatropic rearrangement to a homologous allylic phenylthioether. The rearrangement is also initiated by ethylidene iodide. Cyclopropanation is not observed. The Simmons-Smith reaction with allylic sulfides results only in formation of an insoluble polymer. 

T. Cohen, M. Bhupathy, Organoalkali Compounds by Radical Anion Induced Reductive Metalation of Phenyl Thioethers, Acc. Chem. Res. 1989, 22, 152-161. 

A useful review of diterpenoid chemistry has appeared.1 Some aspects of the distribution of diterpenoids in plants have been discussed.2 An interesting feature of the new diterpenoids described over the past few years is the increase in the number with skeleta based on the macrocyclic ring formed by the cyclization of geranylgeranyl pyrophosphate at the distal double bond. This mode of cyclization has formed the basis of a biogenetically patterned synthesis3 of ( )-nephthenol (2) and ( )-cembrene A from the distal epoxide of geranylgeranyl phenyl thioether (1). 

The protocol for this tandem cyclization involves deprotonation of allylic phenyl thioethers such as 218136. The authors observed that transmetalation with LiBr was required to obtain high yields of the cyclization product. Conversion of the resulting allyllithium 219 to the monocyclic intermediate 220 followed by intramolecular displacement of the thiophenoxide ion efficiently afforded the fused vinylcyclopropane 221 (Scheme 66). Formation of the five-membered ring was quantitative, starting from a substrate in which both alkene functions were monosubstituted126. 

In this context Cohen and coworkers have reported that a homoaflyllithium, generated by reductive lithiation (see below) from phenyl thioether 153, adds to a-methylstyrene and the resulting benzyllithium is able to cyclize, giving rise to sesquiterpene ( )-cuparene (Scheme 43)77. 

---