Hydrogen 3-nitrophthalates, from

CgHaNOs) 3-Nitrophthalic anhydride F. Loss of hydrogen cyanide from metastable ions indicates that molecule lost is HC N. indicates that molecule lost is H CN. indicates that molecule lost is DCN. 110 g, m 116... 

The derivative selected in any particular instance should be one which clearly singles out one compound from among all the possibilities and thus enables an unequivocal choice to be made. The melting points of the derivatives to be compared should differ by at least 5-10°. Whenever possible, a derivative should be selected which has a neutralisation equivalent as well as a melting point (e.g., an aryloxyacetic acid derivative of a phenol. Section IV,114,4, or a hydrogen S nitrophthalate of an alcohol. Section 111,25,5). 

Heat 3-nitrophthalic anhydride with ammonium carbonate to get 3-nitrophthalimide (I). Dissolve 4.3 g (I) in 50 ml 90% methanol and add 1.9 g sodium borohydride over 30 minutes while stirring vigorously at room temperature. Stir 2 hours, acidify with 20% HCI, evaporate in vacuum and treat the dry residue with acetone. Evaporate in vacuum to get 3.9 g (88%) 3-OH-4-nitrophthal-imidine (II) (recrystallize from acetone). Dissolve 3.9 g (II) in 40 ml 20% HCI and stir for 10 hours on water bath at 80-90°. Distill off HCI and stir residue with acetone. Filter and evaporate in vacuum to get 3.4 g 3-OH-4-nitrophthalide (III) (recrystallize from CHC 3 and can purify on column). Prepare an ether solution of CH2N2 and add to 1.93 g (III) in a 100 ml flask until a reaction is no longer evident. Add acetic acid to decompose excess diazomethane and evaporate in vacuum to get about 2 g of 2-methoxycarbonyl-6-nitrostyrene oxide (IV) (can purify on column). Dissolve 560 mg (IV) in 50 ml absolute methanol, add 50 mg Pt02 and hydrogenate as described elsewhere here (other reducing methods should work). Filter,... 

The synthesis of ionic triiodinated contrast agents starts from either bisamino nitrophthalic acid or amino isophthalic acid. The nitro group is reduced to the amino moiety by hydrogenation. Iodine is introduced in aqueous solution with iodine monochloride. Due to the decrease in solubiHty the resulting triiodobenzene precipitates from the solution and can be recrystallised. Amino functions are then acylated. 

Phthalic anhydrides readily form hydrogen phthalate esters on reaction with alcohols the derivatives from 3-nitrophthalic anhydride are usually nicely crystalline compounds and are hence suitable for purposes of characterisation. Hydrogen phthalate esters are also useful in appropriate instances for the resolution of racemic alcohols (Section 5.19). 

If, when the product is cooled, the hydrogen 3-nitrophthalate does not crystallize, extract it with saturated sodium bicarbonate solution and acidify the extract with 2N hydrochloric acid. Recrystallize from aqueous alcohol. 

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