A Uracil to Substituted Benzene Transformation

Refluxing of l,3-dimethyl-5-formyluracil with acetylacetone in ethanolic sodium ethoxide for 2 hours followed by acidification of the mixture with concentrated hydrochloric acid gives ethyl 3-acetyl-4-hydroxybenzoate in 55% yield, together with 1,3-dimethylurea. 

Japanese workers have studied this transformation, and postulated two very reasonable mechanisms. When the deuterated uracil Het-CDO was used, the product was ethyl 3-acetyl-2-deuterio-4-hydroxybenzoate, in full agreement with one of their suggested mechanisms. Their alternative mechanism would have led to the isomeric ethyl 3-acetyl-6-deuterio-4-hydroxybenzoate. 

Identify a reaction mechanism which is consistent with the results of the labelling study. 

Reaction of vinyl sulfoxides with dichloroketene has been found to result in a new general synthesis of y-lactones. With phenyl ( P-styryl sulfoxide, for example, the product, obtained in 65% yield, is the lactone 1. 

Treatment of 7V-(2-hydroxy-2-phenylethyl)-2-aminomethylthiophene with polyphosphoric acid results in formation of 4-phenyl-4,5,6,7-tetrahydrothieno[2,3-c]pyridine (1) in 89% yield. If trifluoroacetic acid is used, however, the product, obtained in 100% yield, is a 4 1 mixture of 7-phenyl-4,5,6,7-tetrahydrothieno[3,2-c]pyridine 2 and 1. 

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