1- Chloro-4- phthalazine

Hydralazine has been prepared by various procedures from 1-chlorophthalazine (2,21,22,24,28), phthalazine-1-thione (20,23,25), 1, 4-dichlorophthalazine (29,30,31), 1-(methylsulfonyl)-phthalazine (27), or 1-cyano-2-benzal acetate (26). Phthalazone, used to prepare 1-chloro-phthalazine, has been prepared from naphthalene (3,28) or from phthalic anhydride (3)- A comprehensive survey on hydrazinophthalazines and related compounds has been published by Druey and Tripod (3)- Some of these procedures are outlined in Figures 9 and 10. 

Hydroxyphthalazin-l(2//)-one is obtained in a smooth reaction between phthalic anhydride and hydrazine hydrate and this is again the starting compound for many 1-substituted and/or 1,4-disubstituted phthalazines. The transformations of 1,4-dichloro-phthalazine, which is prepared in the usual manner, follow a similar pattern as shown for pyridazines in Scheme 110. On the other hand, phthalonitrile is the preferential starting compound for amino- and hydrazino-phthalazines. The most satisfactory synthesis of phthalazine is the reaction between a,a,a, a -tetrachloro-o-xylene and hydrazine sulfate in sulfuric acid (67FRP1438827), alt iough catalytic dehalogenation of 1-chloro- or 1,4-dichloro-phthalazine or oxidation of 1-hydrazinophthalazine also provides the parent compound in moderate yield. 

A general approach to rhenium hydrazido complexes is the reaction of oxo or chloro compounds with organohydrazines as has been demonstrated in an early report with the synthesis of [Re NNC(Ph)0 Cl2(PPh3)2] (310), " the molecular structure of which was solved in 1988. A detailed study on [Re(NNR)Cl2(PPh3)2] complexes with R = COPh or phthalazine shows that the course of subsequent reactions is governed both by the nature of the donor group R responsible for chelate closure and by the type of donor ligand introduced. No simple substitution chemistry has been observed for R = phthalazine. The benzoyl compound... 

The freshly obtained yet moist chloro compound is heated on the water bath for two hours in a mixture of 100 parts by volume of ethyl alcohol and 90 parts by volume of hydrazine hydrate. Preferably after filtering, 1-hydrazine-phthalazine crystallizes out in yellow needles on cooling. 

Phthalazine 6-Chloro-4-(ethoxycar-bonyl-methyl)-l-hydroxy- E9a, 760 [3-(COOR — methylen) —... 

As alternatives to the chloro compounds for substrates in nucleophilic displacement reactions, phenoxy compounds and cyclic amides and cyclic thioamides have been used. It appears that 2-phenoxyquinoxaline is significantly less reactive than the corresponding cinnoline or phthalazine derivatives and only gives a negligible yield of 2-aminoquinoxaline when heated with ammonium acetate. However the phenoxyquinoxaline 1 is converted in high yield into the aminoquinoxaline 2 on treatment with this reagent. ... 

Ch. 5 4-Chloro-, 4-Alkoxy-, and 4-Phenoxycinnolines 6 Aminocinnolines 7 Cinnoline Quaternary Salts 8 Reduced Cinnolines Ch. 9 Cinnolines Containing Additional Fused Rings Ch. 10 Phthalazines Unsubstituted in the Hetero Ring Ch. 11 l-AUcyl-, 1-Aryl-, and 1,4-Diarylphthalazines Ch. 12 1-Hydroxyphthalazines... 

In contrast, the unsymmetric substrate, 3-chloro-5,7,12,14-tetrahydrophthala-zino[2,3-b]phthalazine-5,12-dione (324, R = Cl), underwent similar oxidative... 

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