2- Methoxy-l,3-dithiane

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. 

Sauriol-Lord and St-Jacques (64) have studied 2,4-benzodithiepin 78 and the substituted derivatives 79-82 (Fig. 14). They found that these compounds exist in the chair form 39 (0=S) (Fig. 8), except for the derivative 82 where 13% of the twist-boat 40 (0=S) was detected. The fact that essentially only the chair form was observed in these compounds would simply be due to the long C - S bonds which attenuate the effects of steric repulsions in conformer 39 (0 =S). This is in accord with the fact that in contrast to 2-methoxy-l,3-dioxane which exists as a 7 3 mixture of equatorial conformer 83 and axial conformer 84, 2-methoxy-l,3-dithiane has been found to exist solely in the axial form 85. 

Ahnlich erhalt man in THF 2-Methoxy-l, 3-dithian [45% Sdp. 6070,1 Torr (13,3 Pa)] durch Umsetzung von Dilithium-1,3-propandithiolat (aus dem Dithiol mit Butyllithium). 

Bis-[ethylthio -methoxy-methan Bis-[ethylthio]-ethoxy-methan Methoxy-methylthio-phenylthio-methan 2-Methoxy-l, 3-dithiolan 2-Methoxy-1,3-dithian 2-Isopropyloxy-l, 3-dithian... 

DIELS-ALDER REACTIONS l,3-Bis(trimethylsilyIoxy)-l,3-butadiene. trans, rnms-1,4-Diacetoxybutadiene. 1,2-Dicyanocyclobulene. Ethyl /fans-1,3-butadiene-I-carbonate. Furane. 2-(2-MethoxyFallylidene-l,3-dithiane. 2-Methoxy-3-phenyIthiobuta-l,3-diene. l-Methoxy-3-trimcthylsilyloxy-l,3-butadiene. Sulfur dioxide. 1-Trimethylsily 1-1,3-butadiene. 2-Trimethylsilyloxy-l, 3-butadiene. 

C7H4IO2 88-67-5) see Chlorprothixene laS-laR (l , 3S ),p/f, 8S ]]-a-(4-iodo-l-methoxy-3-methylbutyl)-P-niethoxy-g-methyl-l,3-dithiane-2-butanol (C, .H7 IOjS2 118246-96 ) see Tacrolimus... 

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