Acetal Acetaldehyde, bromo-, diethyl

Acetaldehyde, bromo-, diethyl ACETAL, 23, 8 24, 3 Acetamide, 25, 36 /i-Acetaminobenzenesulfinate, SODIUM, 22, 31... 

A -(2 2-Diethoxyethyl)anilines are potential precursors of 2,3-unsubstituted indoles. A fair yield of 1-methylindole was obtained by cyclization of N-inethyl-M-(2,2-diethoxyethyl)aniline with BFj, but the procedure failed for indole itself[2], Nordlander and co-workers alkylated anilines with bromo-acetaldehyde diethyl acetal and then converted the products to N-trifliioro-acetyl derivatives[3]. These could be cyclized to l-(trifluoroacetyl)indoles in a mixture of trifluoroacetic acid and trifluoroacetic anhydride. Sundberg and... 

The synthesis of benzo[6]thiophenes by the PPA-promoted cyclization of (arylthio)acetaldehyde dimethyl or diethyl acetals [Eq. (4)] was introduced by Tilak287, 288 in 1950 and improved in 1951.289 The acetals are readily prepared from aryl mercaptans and bromo-acetaldehyde dimethyl (or diethyl) acetal in the presence of sodium ethoxide, or by reaction of an aryllithium compound with [(MeO)2CHCH2S]2.290 Diethyl acetal as starting material sometimes gives better yields of product than the corresponding dimethyl acetal.291 Optimum yields of benzo[6]thiophenes are obtained when cyclization of the acetals is carried out under reduced pressure so that the lower boiling benzo[6]thiophenes distill as soon as they are formed. Experimental conditions for obtaining optimum yields vary from case... 

The diethyl acetals of acetaldehyde, propionaldehyde, isobutyraldehyde, and butyraldehyde are converted into at-bromo acetals when treated at 25-40° in sunlight or under irradiation by a 60 W lamp with A-bromosuccinimide added portionwise 651 the reaction being exothermic, cooling is required. This method gives purer products than do those described above, but the yields are no better. 

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