2- -l ,3-dithiolane

Fourteen derivatives of spiro[(2/7-l-benzopyran)-2,2 -l, 3 -dithiolane] (118) were prepared (64-81% yield) and studied. They existed in solution as the spiro form, exhibiting observable photocoloration only at -100°C. The colored forms ( a.max usually in the 600-615-nm region) were readily decolorized upon heating or irradiating with visible light. Their spectra underwent hypsochromic shifts upon introduction of a donor (alkoxy) substituent in the 7-position, annellation of a benzene ring to the 5,6- positions, or replacement of the sulfur atoms with oxygen atoms.130... 

SYNS C 13963 C-13963 CARBAMIC ACID, DIMETHYL-, 2-(l,3-DITHIOLAN-2-YL)PHENYL ESTER CARBAMIC ACID, DIMETHYL-, o-(l,3-DITHIOLAN-2-YL)PHENYL ESTER... 

Starting from hydroxybenzaldehydes, several workers prepared independently phenylcarbamates the phenyl group of which contains cyclic acetal (1,3-dioxolane) and cyclic mercaptal (1,3-dithiolane) groups (Nikles et al., 1966 Nikles, 1969 Durden and Weiden, 1969 Bachmann and Legge, 1968). Of the former, 2-(l,3-dioxolan-2-yl)-phenyl N-methylcarbamate, dioxocarb (22), and of the latter, 2-(l,3-dithiolan-2-yl)-phenyl N-methylcarbamate, (23) attained practical importance. 

A soln. of methyl 9,10-dihydrolysergate and methyl formate in chloroform stirred and treated with ethane-1,2-dithiol, then a soln. of TiCl4 in abs. chloroform added rapidly, and stirred 60 hrs. at room temp. methyl 2-(l,3-dithiolan-2-yl)-9,10-dihydrolysergate. Y 96%. F. e. by related methods s. P. Stiitz and P. A. Stadler, Helv. 55, 75 (1972). 

Aromatics containing electron releasing groups such as phenols, dim ethyl am in oben 2en e and indole are formylated by 2-ethoxy-l,3-dithiolane in the presence of boron trifluoroetherate, followed by hydrolysis (114). The preformed dithiolanium tetrafluoroborate also undergoes Friedel-Crafts reaction with aromatics such as dim ethyl am in oben 2en e and indole (115), and was used to generate dithiolanium derivatives (formyl precursors) from the enoltrimethylsilyl ether derivatives (116). 

The preparation of e/n-difluoro compounds by the oxidative fluorodesul-furization ot 1,3-dithiolanes readily proceeds by treatment with a pyridinium polyhydrogen fluoride-Af-halo compound reagent the latter serves as a bromonium ion source [2], l,3-Dibromo-5,5-dimethylhydantoin is the most effective of several At-halo oxidants. It is believed that /V-halo compounds combine with hydrogen fluoride to generate in situ halogen fluorides, the oxidants. Formation of gem-difluorides from dithiolanes derived from ketones is efficient and rapid, even at -78 °C, whereas the reaction of dithiolanes derived from aldehydes requires higher temperature (0 °C) (equation 4). 

Thiocarbonyl compounds can be converted into difluoromethylene compounds usually under milder conditions than the conesponding carbonyl compounds Ethylene trithiocarbonate reacts smoothly with sulfur tetrafluoride at 110 °C in the absence of catalyst to give 2,2-difluoro-l,3-dithiolane in high yield. Thiuramsul/ides under similar conditions are readily converted into dialkyItrifluo-rometkylamines [11] (equations 13 and 14). 

Catalytic hydrogenation of (4 V,6 / ,9 a5)-4 -phenyl-6 -propylhexahydros-piro[l,3-dithiolane-2,8 (l //)-pyrido[2,l-c][l,4]oxazin]-l -one over Raney Ni in MeOH gave (4V,62 ,9a5)-4-phenyl-6-propylperhydro[2,l-c][l,4]oxazin-l-one (OOJOC4435). 

The pivotal step in this sequence is an electrophilic substitution on indole. Although the use of l,3-dithian-2-yl carbanions is well documented, it has been shown only recently that 1,3-dithian-2-yl carbenium ions can be used in a Priedel-Crafts type reaction. This was accomplished initially using 2-methoxy-l,3-dithiane [1,3-Dithiane, 2-methoxy-] or 2-metlioxy-l,3-dithiolane [1,3-Dithiolane, 2-methoxy-] and titanium tetrachloride [Titanate(l —), tetrachloro-] as the Lewis acid catalyst.9 2-Substituted lysergic acid derivatives and 3-substituted indoles have been prepared under these conditions, but the method is limited in scope by the difficulties of preparing substituted 2-methoxy-1,3-dithianes. l,3-Dithian-2-yl carbenium ions have also been prepared by protonation of ketene dithioacetals with trifluoroacetic acid,10 but this reaction cannot be used to introduce 1,3-dithiane moieties into indole. 

Zur Reduktion von Thiohamstoff und 2-Thiono-l,3-dithiolan bzw. deren Selen-Ana-logen s. S. 677. 

Ethynylquinoxalme (144) and bis(isopropoxythiocarbonyl) disulfide (145) gave 2-(2-oxo-l,3-dithiol-3-yl)quinoxalme (146) [l,l -azo(cyclohexanecar-bonitrile), PhMe, reflux, N2, 7 h 77%] somewhat similarly, 2-(acetylethy-nyl)quinoxaline and 4-phenyl-l,3-dithiolane-2-thione gave 2-(5-acetyl-2-... 

Thioxo-l,3-dithiolan-4-yl)quinoxaline (38) gave 2-(l-methylthiovinyl)qui-noxaline (39) (NaOH, H2O, MeOH, reflux, 1 min then Melj, 20°C, 5 min ... 

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

In the synthesis of l,3-dithiolan-2-ones from spirocyclic intermediates, via episulfides, substituted tetrathiacyclododecane and the related pentathiacyclopentadecane were isolated in good yields <96JCS(P1)289>. Preparation and molecular dynamics studies of 2,5,8,17,20,23-hexathia[9.9]-p-cyclophane have been reported <96P4203>. The syntheses and properties of thiocrowned l,3-dithiole-2-thiones and their conversion to tetrathiafiilvenes via treatment with triethylphosphine have been described <96LA551>. 

---