1, 3-Dichloro-2-butene

Catalytic asymmetric methylation of 6,7-dichloro-5-methoxy-2-phenyl-l-indanone with methyl chloride in 50% sodium hydroxide/toluene using M-(p-trifluoro-methylbenzyDcinchoninium bromide as chiral phase transfer catalyst produces (S)-(+)-6,7-dichloro-5-methoxy-2-methyl-2--phenyl-l-indanone in 94% ee and 95% yield. Under similar conditions, via an asymmetric modification of the Robinson annulation enqploying 1,3-dichloro-2-butene (Wichterle reagent) as a methyl vinyl ketone surrogate, 6,7 dichloro-5-methoxy 2-propyl-l-indanone is alkylated to (S)-(+)-6,7-dichloro-2-(3-chloro-2-butenyl)-2,3 dihydroxy-5-methoxy-2-propyl-l-inden-l-one in 92% ee and 99% yield. Kinetic and mechanistic studies provide evidence for an intermediate dimeric catalyst species and subsequent formation of a tight ion pair between catalyst and substrate. 

Enantioselective Robinson annelation Alkylation of indanone 2 with 1,3-dichloro-2-butene (E/Z = 4 1) catalyzed by 1 gives (S)-3 in 92% ee. The enantiomer, (R)-3, is obtained by the same alkylation but catalyzed by N-(/ -trifluoro-methylbenzyl)cinchonidinium bromide in 78% ee and 99% yield. Optically pure 3 undergoes hydrolysis and cyclization in high yield. Demethylation and alkylation provides the desired tricyclic enone 4 in 83% overall yield from (R)-3. 

In a 3-1. three-necked round-bottomed flask fitted with a reflux condenser and a mercury-sealed stirrer, 250 g. (2 moles) of 1,3-dichloro-2-butene (Note 1) and 1.25 1. of 10% sodium carbonate are heated at reflux temperature for 3 hours. The 3-chloro-2-buten-l-ol is extracted with three 300-ml. portions of ether, which are then dried over anhydrous magnesium sulfate. The ether is removed by distillation through a 20-cm. Fenske column, and the residue is distilled from a 250-ml. Claisen flask, yielding 134 g. (63%) of 3-chloro-2-buten-l-ol, b.p. 58-60°/8 mm., 1-4670. 

Dichloro-2-butene was obtained from Eastman Kodak Company. Redistillation of the crude material did not appreciably alter the yield in the first stage of the reaction. 

Allylation of potassium enoxyborates (11. 506)." This reaction can be used to prepare 1.4- and 1,5-diketones by allylation with 2,3-dichloropropene or 1,3-dichloro-2-butene followed by hydrolysis of the vinyl chloride group (9, 294). 

Asymmetric Robinson Annulation. 2-Propyl-1-indanone undergoes Robinson annulation with the catalyst and methyl vinyl ketone (eq 6). Higher ee values were achieved using 1,3-dichloro-2-butene (Wichterle Reagent) as an MVK surrogate for the Michael addition and overall Robinson annulation (eq 9)... 

Ethylene glycol also serves as an efficient solvent for the production of mono-vinylacetylene by the dehydrochlorination of 1,3-dichloro-2-butene with potassium hydroxide in a flask fitted with a Friedrichs condenser and aTruebore stirrer carry-... 

Dichloro-2-butene [1, 214-215], Change suppliers to read Aldrich (pure) Eastman (pract.). 

Annelation 1,3-Dichloro-2-butene. 2,3-Dimethyl-2-butylborane. 3,5-Dimethyl-4-chloro-methylisoxazole. Methyl vinyl ketone. /ram-3-Pentene-2-one. Pyrrolidine. 

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