Phthalazine-diol

A novel formal inverse-electron-demand hetero-Diels-Alder reaction between 2-aryl-a,/3-unsaturated aldehydes and ketones produces dihydropyran derivatives stereo-specifically.161 The inverse-electron-demand Diels-Alder reaction of 3,4-r-butylthio-phene 1-oxide with electron-rich dienophiles shows vyn-jr-face and endo selectivity.162 (g) The inverse-electron-demand Diels-Alder reaction of dimethyl l,2,4,5-tetrazine-3,6-dicarboxylate with a variety of dienophiles produces phthalazine-type dihydrodiol and diol epoxides which were synthesized as possible carcinogens.163... 

The first catalytic version of this dihydroxylation used 4-chlorobenzoate esters 1 b/2b4. Since then, 2-methoxyphenyl-1 c/2c, 9 -phenanthryl- ld/2d, and 4 -methyl-2 -quinolyl esters le/2e have been reported5. A major improvement came with the phthalazine-l,4-diol derivatives... 

Dimethyl l,2,4,5-tetrazine-3,6-dicarboxylate continues to be an important reagent in the inverse Diels-Alder reaction, and has been used in the synthesis of ningalin D <05JA10767>, dihydrodiol and diol epoxide of phthalazine <05T1545> and novel pyridazino-psoralen derivatives <05T4805>. 

Possibly carcinogenic dihydrodiols and a diol epoxide of phthalazine, viz. 207 and 208, were obtained by cycloadditions of the corresponding aromatic dihydro diols 203 and tetrahydro diol epoxide 204 to dimethyl... 

Asymmetric monodihydroxyiation of 1,3-dienes. This osmylation can be effected with use of [l,4-bis(9-0-dihydroquinidinyl)phthalazine (1) as the ligand. In this reaction the products with few exception are ene diols generally osmylation occurs with the more electron-rich double bond. Some regioselectivity is observed with nonconjugated dienes, with a preference for trisubstituted double bonds over terminal ones. 

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