1.3- Oxathiolane-2-thiones

The 2-imino-l,3-oxathiolanes (43) may be prepared by reaction of isothiocyanates, RNCS, with either (310) <77BCJ3271> or (311) <74JOM(72)103>, and reaction of the latter with CSj gives 1,3-oxathiolane-2-thione (42). 

To a stirred solution of carbon disulfide (CS2,1 0.35 g, 5 mmol) in methanol (0.064 g, 2 mmol) containing NaH (10 mol%), was added the oxirane derivative (2 2 mmol) at room temperature. The mixture was then stirred for 12 h, and filtered to remove the white precipitates (presumably, NaOMe). The residue was purified by extraction with diethyl ether to afford pure 1,3-oxathiolane-2-thione 3. All the compounds were characterized by spectral and analytical studies. 

Scheme 100 Cationic polymerization of 5-benzoxymethyl-1,3-oxathiolane-2-thione.

Lewis acid SnCLj-assisted reaction between the l,3-thiazole-5-thione 434 and /ra r-2,3-dimethyloxirane led to the m 4,5-dimethyl-l,3-oxathiolane 435 The same Lewis acid enabled a second addition of /ra/ -2,3-dimcthyloxirane onto the C—N bond of the 1,3-thiazole ting of 434, leading to the formation of the tetrahydro-2//-thiazolo[2,3- ]-oxazole adduct 436 (Equation 200) <2000HCA3163>. Condensation of 2,4-dinitroimidazole, 8-bromotheophylline, and 8-bromoadenine with substituted methyloxiranes involved sequential A -alkylation-r/wo-substitution and furnished a series of 2,3-dihydro-imidazo[2,l- ]oxazole derivatives 437, 438, and 439 (Equations 201-203) <2000CCC1126, 2000EJ03489, 2005TL3561, 2004JHC51>. 

Reaction of thiazoline-5-thiones with epoxycycloalkenes to give spiio thiazoline/oxathiolane products 75 has been described <99HCA1458> and intramolecular hetero Diels-Alder reactions based on 1,3-oxathiolane 5-oxides such as 76 going to 77 have been reported <98MI2733>. 

Under basic conditions, oxiranes react with carbon disulfide exothermically, as shown in Scheme 34, to yield l,3-oxathiolane-2-thiones. The reaction appears to be quite general although no examples have appeared outside of the patent literature. 

A review on reactions of 2-alkylidenethiiranes includes their reaction with carbonyl compounds, R32C=0, to give 4-alkylidene-l,3-oxathiolanes 88 <07S2755>, and synthesis of the polyether-bridged bis(l,3-oxathiolane-2-thiones) 89 from the corresponding bis(epoxides) and CS2 with catalytic LiBr has been described <07PS2419>. A convenient... 

Ketene itself reacts with l,2-dithiole-3-thiones with formation of a 1,3-dithiolane derivative.211,212 In the same manner a l,2-dithiol-3-one gives a 1,3-oxathiolane derivative (147). 

The simple 1,3-oxathiolane systems for which IR data are available include 2-methyl-l,3-oxa-thiolane <59acil04>, l,3-oxathiolan-5-one (33) with a CO absorption at 1771 cm" <76ACS(A)457>, and l,3-oxathiolan-2-one (32), its isomer (28) and the thione (42) whose spectra have been compared <69JOC30ii>. The 1,3-oxathiolane 3,3-dioxides have a characteristic pair of absorptions due to the SO2 group which occur at 1320 cm" and 1130 cm" for (41) and at 1300 cm" and 1140 cm" for the benzo derivative (23) <66RTC323>. 

The parent 2-imino-l,3-dioxolane (29 R = H) was first prepared by reaction of the Af-chloro analogue with NaNH2 in liquid ammonia <74JOC3442> and the formation of A -substituted analogues is best achieved from the tin compound (300) and an isothiocyanate as described in Section 3.10.8.2. The sulfur analogue (310) similarly gives good yields of the 2-imino-1,3-oxathiolanes by reaction with isothiocyanates and of l,3-oxathiolane-2-thione (42) with CS2. An early but efficient preparation of... 

Monothioacetals 1,3-Oxathiolanes Thiolactams S extrusion, 59-60, 261 Thiols synthesis from haloalkanes, 169, 269 Thionation of lactones, 110-111 Thiones olefination of, 35 Thionocarbonates. See Carbonothioates Thionolactones, 110-111 Thionyl chloride prepn. of acyl halides, 143 prepn. of carboxylic esters, 347 prepn. of haloalkanes from alcohols, 32 Thiophenoi. See Benzenethiol Thiotosylatc. See Benzenesulfonothioic add... 

A facile synthesis of 5-(2-thioxo-l,3-dithiolan-4-yl)methyl dialkylcarbamothioates and 5-thiiran-2-ylmethyl dialkylcarbamothioate from reaction of 5-(chloromethyl)-l,3-oxathiolane-2-thione with sodium dialkylcarbamodithioate and dialkylamine, respectively, has been reported to co-occur via intermolecular 0-S rearrangement (Scheme 81). " ... 

The condensation of aldehydes with thiocyanoacetic esters, catalysed by potassium fluoride or potassium carbonate, gave as minor products yV-carbamoyl-2-imino-5-alkyl(or aryl)-l, 3-oxathiolan-4-carboxylic esters, in which the 4,5-c/j-isomers predominated according to n.m.r. spectroscopy. l,3-Oxathiolan-2-thione was converted into dimethyl 1,3-dithiol-2-one-4,5-dicarboxylate and ethylene on treatment with dimethyl acetylene-dicarboxylate, and the transformation of methyl 2-methoxycarbonyl-methyl-1,3-oxathiolan-2-carboxylate into dimethyl-5,6-dihydro-l, 4-oxa-thiin-2,3-dicarboxylate by chlorination at low temperatures found analogy in the reactions of 2,2-dialkyl-l,3-oxathiolans. Thiomethoxymethyl hexachloroantimonate reacted with potassium t-butoxide to give mainly 3,5,5-trimethyl-l,3-oxathiolanium hexachloroantimonate the mechanism of this remarkable reaction was not settled. ... 

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