- The use of aminoiminomethanesulfinic acid (thiourea dioxide) under phase transfer conditions for generating organochalcogenate anions. Synthesis of sulfides, selenides and tellurides
-
A procedure is described which allows for the in situ synthesis of arylalkyl, diaryl and dialkylchalcogenides under phase transfer conditions starting from the corresponding diorganodichalcogenides.The dichalcogenides are reduced by aminoiminomethanesulfinic acid (thiourea dioxide) in alkaline medium and catalyzed by a quaternary ammonium salt.The reduction proceeds easily for diaryl disulfides and diaryl diselenides at a sodium hydroxide concentration of 13percent; diaryl ditellurides require a 50percent sodium hydroxide solution to give the aryl tellurolate anion.The dialkyl diselenides and dialkyl ditellurides are more difficult to reduce.The intermediate arylthiolates and arylselenolates are quenched by alkyl and activated aryl halides to give the corresponding sulfides and selenides in high yield (77-97percent).The aryltellurolates react with alkyl halides giving the aryl alkyl tellurides in 81-96percent yield.The procedure could not be successfully used for the synthesis of dialkylselenides and dialkyl tellurides; low yields and mixture of products were formed.
- Comasseto, J. V.,Lang, E. S.,Ferreira, J. Tercio B.,Simonelli, F.,Correira, V. R.
-
p. 329 - 340
(2007/10/02)
-
- Oxidation of Alkyl Phenyl Selenides, Tellurides, and Telluroxides with meta-Chloroperbenzoic Acid for a Facile and Novel Transformation of C-Se and C-Te Bonds to C-O Bonds
-
In sharp contrast to the well-known selenoxide elimination leading to olefins, the treatment of alkyl phenyl selenides (PhSeR) with an excess of meta-chloroperbenzoic acid (MCPBA; 2-5 equiv. to a selenide) in alcohol at room temperature affords the corresponding dialkyl ethers by the substitution of a phenylselenium (PhSe) moiety with an alkoxy group.A similar reaction proceeds by using alkyl phenyl tellurides (PhTeR) and telluroxides , a facile substitution of PhTe or PhTe(O) moiety by an alkoxy group being observed.Methanol is the most appropriate solvent for these oxidations and alkyl methyl ethers are formed in excellent yields.The reaction is accompanied by phenyl migration when applied to some selenides, tellurides, and telluroxides having a phenyl group at a vicinal position to the PhSe, PhTe, or PhTe(O) moiety.Application to the methoxyselenation and methoxytelluration products of cyclohexene and cycloheptene results in a ring-contraction to afford the dimethyl acetals of cyclopentane- and cyclohexane-carbaldehyde, respectively.In case of an allylic phenyl selenide, a sigmatropic rearrangement giving a rearranged allylic alcohol occurs in much preference to the substitution by the methoxy group.Other oxidizing agents than MCPBA such as NaIO4, H2O2, t-BuOOH, and ozone are generally ineffective under similar conditions.It is proposed that the reaction mainly takes place as follows.Alkyl phenyl selenone, alkyl phenyl tellurone, or the MCPBA addition product to them is formed as a reactive intermediate in which an alkyl C-Se or alkyl C-Te bond fission occurs heterolytically by a nucleophilic attack of alcohol, sometimes accompanied by a 1,2-shift of the β-substituent, i.e., phenyl migration and ring-contraction.
- Uemura, Sakae,Fukuzawa, Shin-ichi
-
p. 471 - 480
(2007/10/02)
-
- ALKALINE HYDROLYSIS OF DIARYL DITELLURIDES UNDER PHASE TRANSFER CONDITIONS; SYNTHESIS OF ALKYL ARYL TELLURIDES
-
The disproportionation reaction of diaryl ditellurides with sodium hydroxide under phase transfer conditions at room temperature is described for the first time.The phase transfer catalyst used is 2HT-75, a trade name for a mixture of dialkyldimethylammonium chlorides.The intermediates aryl tellurolates react "in situ" with alkyl halides to give the corresponding alkyl aryl tellurides (ArTeR) in 52-72percent yield.The following compounds were prepared: Ar = C6H5, R = CH3(CH2)3CH2,(CH3)2CHCH2CH2, (CH3)2CHCH2, CH3CHBrCH2CH2, CH3(CH2)8CH2, C6H5CH2, ClCH2, C6H5CH2CH2, CH2=CHCH2, C6H5CH=CHCH2, C6H5SeCH2, ; Ar = p-CH3C6H4, R = CH3(CH2)2CH2; Ar = p-CH3OC6H4, R = CH3(CH2)2CH2; Ar = p-C2H5OC6H4, R = CH3(CH2)2CH2; Ar = 2-naphthyl, R = CH3(CH2)2CH2.
- Comasseto, J. V.,Ferreira, J. T. B.,Val, Fontanillas
-
p. 261 - 266
(2007/10/02)
-