4- Methoxy-2- -phthalazinone

When large groups, such as phenyl, bromo, ethoxycarbonyl or nitro are attached at position 3, the principal products are l-alkylcinnolin-4(l/f)-ones. Cyanoethylation and acetylation of cinnolin-4(l/f)-one takes place exclusively at N-1. Phthalazin-l(2/f)-ones give 2-substituted derivatives on alkylation and acylation. Alkylation of 4-hydroxyphthala2in-l(2/f)-one with an equimolar amount of primary halide in the presence of a base leads to 2-alkyl-4-hydroxyphthalazin-l(2/f)-one and further alkylation results in the formation of 4-alkoxy-2-alkylphthalazinone. Methylation of 4-hydroxy-2-methyl-phthalazinone with dimethyl sulfate in aqueous alkali gives a mixture of 4-methoxy-2-methylphthalazin-l(2/f)-one and 2,3-dimethylphthalazine-l,4(2//,3//)-dione, whereas methylation of 4-methoxyphthalazin-l(2/f)-one under similar conditions affords only 4-methoxy-2-methylphthalazinone. 

Phthalazin-1 (2H)-one, 4-hydroxy-2-methyl-methylation, 3, 17 Phthalazin-l(2H)-one, 4-methoxy-methylation, 3, 17 Phthalazinones in thermography, 1, 392 Phthalazin-l(2H)-ones alkylation, 3, 17 reaction... 

Chlorophthalazine is quite reactive to many basic nucleophiles but reacts sluggishly with aqueous or alcoholic alkali. In contrast, it is very rapidly hydrolyzed by warm, concentrated hydrochloric acid as are its diazine isomers. In hydrolysis with very dilute acid or with water, it forms some phthalazinone but mostly the self-con-densation product which hydrolyses to give 2-(l -phthalazinyl)-phthalazin-l-one (70% yield). Such self-condensations in diazanaph-thalenes and in monocyclic azines are always acid-catalyzed (Sections II, C and III,B). With methanolic methoxide, 1-chlorophthalazine (65°, few mins), its 7-methoxy analog (20°), and 1,6- and 1,7-dichlorophthalazines (20°) readily undergo mono-substitution. 

Like the corresponding carboxylic acids, these substrates give 4-aIkyl(or aryl)-l(2//)-phthalazinone. However, the esters are seldom used simply because the acids are usually made more easily. An example of the use of keto esters is the condensation of ethyl 2-(2-methoxy-l-naphthoyl)benzoate (95) with hydrazine to afford 4-(2-methoxynaphthalen-l-yl)-l(27/)-phthalazinone (96) (neat H2NNH2-H2O, reflux, 4h 94%). ... 

Hydroxy-6,7-dimethoxy-l,3-dihydro-l-isobenzofuranone (215) gave 7,8-di-methoxy-2-methyl-l(2//)-phthalazinone (216) (MeNHNH2, EtOH, reflux. 

Hydroxymethyl-7-methoxy-l(2H)-phthalazinone gave 4-hydroxymethyl-1,7 (27/,37/)-phthalazinedione (AICI3, PhH, reflux see original for further details). ... 

Dimethylaminoacryloyl)methoxy] -1 (2//)-phthalazinone (138) condensed with ethyl acetoacetate and ammonia (supplied as ACONH4) to give 4-[(5-ethoxycarbonyl-6-methylpyridin-2-yl)methoxy]-1 (2//)-phthalazinone (139) (reactants, AcOH, reflux, <2h 60%). ° " ... 

Chloromethyl-7-methoxy-1 (2H)-phthalazinone l-Chloro-4-(A -methyl-A -methylenehydrazino)phthalazine 1 -Chloro-3-methyl-4-methylimino-3, 4-dihydrophthalazine... 

Diethylaminoethyl)-l(2//)-phthalazinethione 2-(2-Diethylaminoethyl)-l(2//)-phthalazinone 4-Diethylamino-7-methoxy-1 (2//)-pbtbalazinone 1 -Diethylaminomethyl-4-hydrazino-6-methoxyphthalazine... 

Methoxy-2-methyl-5-nitro-1 (2/7)-phthalazinone 4-Methoxy-2-methyl-8-nitro-1 (2/7)-phthalazinone 2-Methoxymethyl- l-oxo-4-pheny 1-1,2-dihydro-6-phthalazinecarbonitrile l-Methoxy-4-methylphthalazine l-Methoxy-4-methylphthalazine 3-oxide... 

Methoxy-1 -pheny Iphthalazine 6-Methoxy-4-phenylphthalazine 4-Methoxy-2-phenyl-1 (2/7)-phthalazinone... 

Methoxy-5,6(l//,27/)-phthalazinedione 1-Methoxyphthalazine 3-oxide 4-Methoxy-1 (2//)-phthalazinone... 

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