Reactions of Nontautomeric Phthalazinones and Phthalaziniumolates

The reductive deoxygenation of nontautomeric phthalazones has been exemph-Aed toward the end of Section 9.2.1. Other reactions of both entities are illustrated in the following classified examples. 

Note Thiation may be effected by phosphorus pentasulfide, Lawesson s reagent (83), or occasionally elemental sulfur. 

2-Phenyl-4-p-tolyl-l(2fl)-phthalazinone (218, X=0) gave 2-phenyl-4-p-tolyl-l(217)-phthalazinethione (218, X = S) (P2S5, xylene, reflux, 30 min 82%).  

2-Phenyl-1,2-dihydro-1 -phthalazinol (220) gave 2-phenyl-1 (2 /)-phthalazi-nethione (221) (S, MeCN, reflux, prolonged 35% clearly involved more than one step) the same substrate (220) gave 2,2 -diphenyl-l,l, 2,2 -tetrahydro-l,l -biphthalazinylidene (222) (AcOH, MeCN, reflux, 2h 48% after purification from other products) and thence the product (221) (neat substrate, S, 270°C, Nj, 20 min 70%).  

Methyl 3-methyl-4-oxo-3,4-dihydro-5-phthalazinecarboxylate (223) gave 9-methyl- 3H-2,9-dihydrophthalazino[3,4,5-rfe]phthalazin-3-one (224) (H2 

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