Methyl-1,3-dithiolanes

Despite the latent reactivity of ketene thioacetals,3-4 some members of this class such as the title compound have been little studied, perhaps because of preparative inaccessibility. The only previously reported route to 2-methylene-1,3-dlthiolane involves monoacetylation of 1,2-ethanedithiol, cyclization to 2-methyl-1,3-dithiolan-2-yl perchlorate, and exposure of this salt to diisopropylethylamine in acetonitrile 5... 

METHYL DIPYRIDO(l,2-a 3, 2 -d)IMIDAZOL-2-AMINE see 7UCS250 (4-METHYL-1.3-DITHIOLAN-2-YLIDENE)PHOSPHORAMIDIC ACID, DIETHYL ESTER see DHH400... 

Cytrolane Diethyl (4-methyl-1,3-dithiolan-2-yiidene)-phosphoramldate... 

METHYL-1,3-DITHIOLAN-2-YLIDENE)-, DIETHYL ESTER PHOSPHORAMIDIC ACID... 

AC 47470 AI3-25991 American Cyanamid CL-47470 CL-47,470 Cyclic propylene (diethoxyphosphinyl)-dithioimidocarbonate Cyclic propylene P,P-diethyl phosphonodithioimidocarbonate Cytrolane (Diethoxy-phosphinyl)dithioimidocarbonic acid cyclic propylene ester 2-(Diethoxyphosphinylimino)-4-methyl-1,3-dithio-lane 0,0-Diethyl(4-methyl-1, idithiolan-2-ylidene)phos-phoramidate 1,3-Dithiolane, 2-(diethoxyphosphinyl-imino)-4-methyl- EI47470 ENT-25,991 HSDB 6411 Imidocarbonic acid, phosphonodithio-, cyclic propylene P,P-diethyl ester Mephosfolan Mephospholan Phosphonodithioimidocarbonic acid cyclic propylene P,P-diethy ester Phosphoramidic acid, (4-methyl-1,3-dithiolan-2-ylidene)-,... 

Diethyl 4-methyl-1,3-dithiolan-2-ylidenephosphoramidate. See Mephosfolan 0,0-Diethyl-0-(5-methyl-6-ethoxy-carbonyl-pyrazolo (1,5-a) pyrimid-2-yl-thionophosphate. See Pyrazophos... 

C3S2 s s — — — l,2-Dithiolane-4-carboxylic acid 3-phenyl-l,2-dithiolylium iodide 4-methyl-1,2-dithiole-3-thione ... 

The modified Sharpless reagent was also successfully applied288 for the asymmetric oxidation of a series of 1,3-dithiolanes 248 to their S-monooxides 249 (equation 134). It was observed that the optical induction on sulphur (e.e. from 68 to 83%) is not significantly affected by the substituents R1 and R2. Asymmetric oxidation of a few aryl methyl sulphides by organic hydroperoxides in the presence of a catalytic amount of the optically active Schiff base-oxovanadium(IV) complexes gave the corresponding sulphoxides with e.e. lower than 40%289. 

Acetylquinoxaline gave its cyclic dithioacetal, 2-(2-methyl-l,3-dithiolan-2-yl)quinoxaline (210a) (HSCHjCHjSH BF3, EtjO, CHCI3, 20°C 14%). ... 

A range of different functional groups has been introduced into the V-position of the C3 side chain, as shown in Table 6.10. A number of different functionalities were shown to be tolerated in this position, with lipophilic groups such as methyl and dithiolane being preferred over polar groups such as ketones and alcohols. Ketone (118) had similar CBi receptor affinity to the unfunctionalised -heptyl compound (84), while alcohol (120) had lower affinity. The phenyl ketone (119) had lower CBi receptor affinity than the simple benzyl-substituted compound (116), but higher CB2 affinity, with about 12-fold selectivity for CB2 over CBi. 

Scheme 1.64). The Ag(I)-mediated cyclization afforded dipole 306 for 1,3-dipolar cycloaddition with methyl vinyl ketone to yield adducts 307 and the C(2) epimer as a 1 1 mixture (48%). Hydrogenolytic N—O cleavage and simultaneous intramolecular reductive amination of the pendant ketone of the former dipolarophile afforded a mixture of alcohol 308 and the C(6) epimer. Oxidation to a single ketone was followed by carbonyl removal by conversion to the dithiolane and desulfurization with Raney nickel to afford the target compound 305 (299). By this methodology, a seven-membered nitrone (309) was prepared for a dipolar cycloaddition reaction with Al-methyl maleimide or styrene (301). 

The simple 1,2-dithiolenes, viz, 1,2-dithiolene (3, R H), 3-methyl-l,2-dithiolene (3, R Me) and the saturated derivative of the latter were detected by Takken and co-workers (2) with crotonaldehyde and butanedione as the starting materials. Ledl (33) identified 2-ethyl-4-methyl-l,3-dithiolene (4) in the reaction mixture containing propionaldehyde, hydrogen sulfide and ammonia, and the isomeric 2,4,5-trimethyl-l,3-dithiolane (5) was obtained by Sultan (29) from the reaction of acetaldehyde, aceto-in, and ammonium sulfide. 

The fluorination of oxathiane is described in Section 25.1.1.3.84 1,4-Dithiane reacts quite differently107 from dioxane and oxathiane over potassium tetrafluorocobaltate(III). The major products (ca. 60 % of the product mixture, itself in ca. 50 % yield) are the result of rearrangement to the 2-methyl-l, 3-dithiolane skeleton, e.g. 1-3. Fluorinated 1,4-dithiancs comprised about 30% of the product the major product is 4. The extent of fluorination, that is the number of fluorine atoms introduced, is much greater than that of dioxane under comparable conditions (tetrahydrothiophene and tetrahydrofuran show a similar contrast). 

A [5 - 2 + 2 + 1] fragmentation followed by cyclization forming a new five-membered ring was observed by FVP studies of 2-propenyl-l,3-dithiolan 1,1-dioxide (79) (95H1967). The reaction mixture consists of four products thiophene (26%), 2,5-dihydrothiophene (80,34%), 4-methyl-2-propenyI-4//-l,3-dithiine (20%), and 2,6-dimethyl-2//,6//-l,5-dithiocine (20%). The last two compounds are formed by [4 + 2] or [4 + 4] dimerization of the intermediate 2-butenethial. Formation of 80 involves a 1,5-H shift of the as-butenethial, followed by cyclization. 

The products of the thermolysis of 3-phenyl-5-(arylamino)-l,2,4-oxadiazoles and thiazoles have been accounted for by a radical mechanism.266 Flash vacuum pyrolysis of 1,3-dithiolane-1-oxides has led to thiocarbonyl compounds, but the transformation is not general.267 hi an ongoing study of silacyclobutane pyrolysis, CASSF(4,4), MR-CI and CASSCF(4,4)+MP2 calculations using the 3-21G and 6-31G basis sets have modelled the reaction between silenes and ethylene, suggesting a cyclic transition state from which silacyclobutane or a trcins-biradical are formed.268 An AMI study of the thermolysis of 1,3,3-trinitroazacyclobutane and its derivatives has identified gem-dinitro C—N bond homolysis as the initial reaction.269 Similar AMI analysis has determined the activation energy of die formation of NCh from methyl nitrate.270 Thermal decomposition of nitromethane in a shock tube (1050-1400 K, 0.2-40 atm) was studied spectrophotometrically, allowing determination of rate constants.271... 

Thiosulfonium ions derived from methylation of substituted 1,2-dithianes (94a) were found to exist in undistorted chair conformation with the methyl group in axial position.254 The phenomenon was interpreted to result from minimizing electron repulsion in orthogonal position (94b) (ab initio calculation at STO-3G //STO-3G level). Unlike 1,2-dithianes, methylation of 1,2-dithiolanes and substituted thianes to form the corresponding. S -methylsulfonium hexafluorophosphate and perchlorate salts255 is non-stereoselective. 

Parent 1,3,5-trithiepane as well as substituted and dithiolane-fused derivatives, useful in synthesis of charge-transfer complexes, were synthesized by cyclocondensation of the corresponding 1,2-dithiols or their salts with di(chloro-methyl) sulfide (see Section 13.16.9.4.1). 

Rhodium-catalysed decomposition of methyl diazoacetate (1.2 equiv.) in the presence of 1,3-dithiolane yields mainly dithiane (31) as a mixture of diastereoisomers.34 Ring-expanded product (32) and ring-opened products (33) arising from a second condensation of the carbene are also isolated, albeit in low yield. Similar reactivity is observed with 1,3-oxathiolane. 

In a new reaction of the Friedel-Crafts type, using 2-methoxy-l,3-dithiolane and a weak Lewis acid such as TiCl4 the ester 45 could be obtained (45). This compound was either hydrolyzed to the 2-formyl derivative or desulfurized with Raney nickel to the 2-methyl compound. 

---