Phenylthio carbene

B. Preparation of Vinyl Sulfides by the Reaction of (Phenylthio)carbenes... 

Phenylthio)carbene,18 a heteroatom-substituted carbene, reacts similarly with a variety of alkoxides to give a-thiomethyl-substituted alcohols 14 (Scheme 8... 

The stereochemistry of the insertion by (phenylthio)carbene to the a C-H bond of trans- and c/s-4-terr-butylcyclohexyloxides 16 was investigated19 to find that the reaction proceeds stereospecifically giving trans and cw-4-rert-butyl-l-methylcyclohexanol 19, respectively, after desulfurization of the primary insertion products 17 (Scheme 9). 

The difference in reactivity between isoprenol and isoprenyloxide, methal-lyl methyl ether and methallyloxide were investigated in the reaction with (phenylthio)carbene generated under phase-transfer conditions. With isoprenol, (phenylthio)methyl ether (41%) was the major product, whereas with methyl ether cyclopropanation (36%) was the sole reaction.1519 With alkoxides, in contrast, the major product was the C-H insertion product (45%) and (phenyl-... 

Table 3. Reaction of (Phenylthio)Carbene with Alkoxides 0...

Phenylthio)carbenoids 26 possessing different chain lengths (Scheme 12, n = 1,2, 3), namely, 4-, 5-, and 6-oxidoalkyl(phenylthio)carbenes (Table 6, entries 1, 7 and 8), undergo similar regioselective cyclization reactions to give 2-(phenylthio)cycloalkanols 27. 

Table 6. Intramolecular Insertion by (Phenylthio)Carbenes into a C-H Bonds of...

This section diverges from the main subject but, being studied together with the insertion of (phenylthio)carbenes with alkoxides, is worth describing here due to its synthetic versatility as C-C bond forming reactions. 

An explanatory mechanism for the formation of vinyl sulfides is shown in Scheme 24. In route a, (phenylthio)carbene 77 generated from chlorosulfide 75 reacts with the nitrile anion to form (phenylthio)carbanion 79, which then undergoes elimination of cyanide ion to produce vinyl sulfide 76. In route b, 75 reacts first with the nitrile anion 74 to produce P-(phenylthio)nitrile 78 followed by base-catalyzed P-elimination. However, route b is unlikely because 79 cannot be generated from 68 due to a larger pKa value of its ot proton than that of the nitrile. In fact, the reaction of chlorosulfide 75a with lithionitrile 80 gave a different product 81 in 63% yield. 

Chloro(phenylthio)carbene [32] has been produced by the standard phase-transfer catalytic procedure from PhSCHCK and trapped by alkenes (see Section 7.3), although the carbene is also prone to dimerization to give [PhS(Cl)C=C(Cl)SPhj. In a similar manner, phenylthiocarbene has been obtained from PhSCH2Cl [33] and chloro(phenoxy)carbene from dichloro(phenoxy)methane [34]. Reaction of the analogous seleno derivatives produce the conesponding phenylselenocarbenes... 

Generation and reaction of chloro(phenylthio)carbene and phenylthiocarbene... 

Phenylthiocarbene, chloro(phenylthio)carbene, their seleno analogues, and the less electrophilic chloro(methylthio)carbene react with a range of alkenes [145-148], as does chloro(phenoxy)carbene [149]. 

Conjugated dienes yield mono-adducts with dihalocarbenes at the more electron-rich C=C bond further reaction at the less reactive bond may also occur [e.g. 4,8,19, 23, 31, 37, 49, 62, 69, 94]. Cycloheptatriene yields the syn- and nnti-1,2 5,6-bis-adducts (14.5 and 22.9%) and the syn-1,2 5,6-ann -3,4-tris-adduct with dichloro-carbene [62], The facile reaction of cyclopropylethenes with dihalocarbenes produces dicyclopropyl compounds [53, 117]. Isoprene reacts with chloro(phenylthio)carbene across the more reactive 1,2-bond (51%) [146]. 

The additions of difluorocarbene onto the bicyclopropylidene derivative 121 (Scheme 24) [116a], of dibromocarbene onto oligospirocyclopropanated bicy-clopropylidenes 56 [33,65] (66% yield) and 62 [117] (94% yield), of dichloro-carbene onto 56 [33] (90% yield), 28a [118] (38% yield) and 121 (99% yield) 1116a] as well as of chloro(phenylthio)carbene (90%yield) [33,1191,of bromo-... 

Preparation of ethylthio-138 and phenylthio-carbene complexes139 was similarly achieved by treatment of the corresponding isolated tetrabutylammonium acylate complexes in CH2C12 at 40 °C with acetyl chloride, then with the corresponding thiols at 0 °C as illustrated in equation 64 for the phenylthio derivatives. 

Evidence for the existence in solution of free bis(phenylthio)carbene, formed by the decomposition of (PhS)3CLi, has been reported. ... 

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