5.6- Dihydropyrido structure

The structures of 6,6-dimethyl-6,7-dihydropyrido[l,2-c]quinazolinium salt (142) (97AJC109), and 6-methyl-9,10-dimethoxy-4-phenyl-... 

The solid state structure of (3>S,8 Sj-10-(8-amino-6-azaspiro[3,4]octan-6-yl)-9-fluoro-3-methyl-7-oxo-2,3-dihydro-7//-pyrido[l,2,3-dfe]-l,4-benzoxa-zine-6-carboxylic acid (218) was determined by X-ray diffraction study (98CPB1710). The structure of 6,10-dihydropyrido[2,l-c][l,4]benzoxazine-6,10-dione 219 was established by X-ray diffraction analysis. It contains a crystal solvate with /j-xylene (99MI40). 

The stereostructure of ethyl OT-4a,7-//-7-phenyl-8-cyano-2-oxo-2,3,4,4a,7,8-hexahydropyrido[l,2-A [l,2]oxazine-8-carboxylate was confirmed by X-ray crystallography. It confirmed a trans-nng junction <20000L4007>. The structure of 2,4-diphenyl-7-o-hydroxyphenyl-5,6-dihydropyrido[2,Ttf]phthalazinium perchlorate 21 has also been established by X-ray crystallographic analysis <1995IZV296>. 

The Structure of a pyrido[l,2-6]cinnoline (17, R = Br) (74JHC125), a pyrido[2,l-a]phthalazine (26) (94T9189), and 2,4-diphenyl-7-o-hydroxyphe-nyl-5,6-dihydropyrido[2,l-fl]phthalazinium perchlorate (27) (95IZV296) have been established by X-ray crystallographic analysis. 

The UV spectrum (7max 235, 270 (sh), 279,301,312, and 378 nm) of 236 indicated a dihydropyrido[4,3-l7]carbazole framework. This assignment was supported by the IR spectrum (v ax 843, 1028, 1167, 1410, 1595, and 1615 cm ). The structure for 3,4-dihydroellipticine was confirmed by synthesis from ellipticine and comparison of the IR and UV spectra, melting points and Rf values. Additional support for this assignment derived from the transformation into derivatives of 3,4-dihydroellipticine (216). 

Asymmetric reduction of carbonyls has also been achieved by Dupas and coworkers by reaction of achiral NADH equivalents mediated by chiral aluminum Lewis acids [23]. They reduced methyl benzoyl formate with the dihydropyrido[2,3-h]indole 86 and chiral aluminum Lewis acids whose structures are drawn and 89 and 90 (Sch. 12). Asymmetric induction was quite low. Details of the reaction, including the conditions used, were not provided nor were the procedures used for the preparation of the chiral Lewis acids 89 and 90. 

It is reported that the formylpyrimidinedione (58) reacts with Schiff bases to yield the dihydropyrido[3,4-rf]pyrimidinediones (60), which are partially hydrolyzed to the triones (61) on workup (89MI1). A likely mechanism (Scheme 8) involves [4 + 2] cycloaddition of the imine to the tautomer (59), followed by dehydration. The trione (61, R = 2-furyl, = Ph) was assigned the structure shown, rather than the regioisomer, which might... 

S. Verma, S.L. Jain, Thiourea dioxide in water a s recyclable catalyst for the s)mthesis of structurally diverse dihydropyrido[2,3-d]pyrimi-dme-2,4-diones. Tetrahedron Lett. 53 (2012) 2595-2600. 

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