3- Alkoxy-2-pyrazolin-5-ones

Alkoxy-2-pyrazolin-5-ones have been prepared by two methods. In one of these a hydrazine is condensed with a -substituted ester (eq. 160).598,1143 The second is O-alkylation of a 4,4-disubstituted-l-... 

Irradiation of 4-hydroxy- and 4-alkoxy-3-pyrazolin-5-one derivatives (163 R = OH, OR) leads to ring cleavage with the formation of /3-diamides (165) 69TL271). The methylene blue sensitized rearrangement of the same pyrazolinone (R = H) to the oxindole (166) also... 

The salicylaldehydes commonly used have nitro, alkoxy, or halogen substituents, and need no further comment. Some unusual ones have cationic substituents 3-, 4- and 5-methylthio- and dimethylaminosalicylaldehydes have been prepared and methylated to the corresponding dimethylsulfonium and trimethylammonium salicylaldehydes. 1012 The salicylaldehyde substituted in the 4-position with a 3,5-diphenyl-2-pyrazolin-l-yl group gives a series of BIPS and spiro(dipyrans) having highly fluorescent spiro forms and nonfluorescent open forms, which is the reverse of the usual situation. 13... 

Most of the syntheses of a-hydroxyalkyl and a-alkoxyalkyl-2-pyrazolin-5-ones have been discussed in connection with the reactions of 2-pyrazolin-5-ones. However, there is one synthesis by which compounds of this type are obtained directly. This is by reaction of the appropriate alkoxy- or phenoxymethylacetoacetic esters with hydrazines (eq. 48).532,1314,1313,1316,1562 The reactions of these compounds... 

A few bis(2-pyrazolin-5-ones) having alkoxy substituents are known and are listed in Table III. These are prepared by addition of alcohols to the double bond connecting the pyrazolinone rings in pyrazole blue. 

A variety of 4-amino-5-alkoxy- and acyloxy-l,3-disubstituted-pyrazoles have been treated with alkylating agents such as alkyl halides to give 4-dialkylamino-3-pyrazolin-5-ones.525 There is a simultaneous alkylation of ring nitrogen and extranuclear nitrogen. 

TABLE XXI. 3-Pyrazolin-5-ones. Alkoxy, Aryloxy, Acyloxy, and Alkylthio Substituents... 

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