Unsubstituted Derivatives

By rxn. of PbCl2 with Me3Al2Cl3 and alkali metal halide in nonpolar solvent or solid state in good yield (1669)  

By electrolysis of MeMgCl with MeCl on Pb anode (if2), in presence of THF and Bu2-carbitole (317), and glycol ethers and aromatic solvent (3I6), in 83-98% yield (77 -78, 781), in (Bu0CH2)s (2271). 

By electrolysis of MeBr in Et4NBr and aq. MeCN on Pb cathode and Pt anode, in 8if% yield (19if6a). 

Electrolytical cell for manufacturing of - (if6, ifl6, 779), Me4Pb recovery after electrolysis (2273)/ MeCl recovery (2272). 

Recovery of Me4Pb from manufacturing process (227if, 2387, 2if70), purification of Me4Pb after manufacturing by treatment with alkane peroxyacid (89), with Qa (888). 

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The rates of reaction of phenacyl bromide with thiosemicarbazide and its phenylated derivative were determined by conductivity measurements in ethanol (517). The reaction is second order up to 85% completion. The activation energies are 10.5 to 11.3 kcal/mole with the phenyl thiosemicarbazide and 8.5 to 9.3 kcal/mole for the unsubstituted derivatives. 

Another source of C-unsubstituted derivatives are o-aminopyridine aldehydes e.g. 216 - 217) (60JCS1370), and the corresponding ketones may be used to furnish C-aryl compounds (71GEP2051013). 

Amino groups are acetylated normally and are converted to hydroxy compounds with nitrous acid. Tlie 2,3-diamino [2,3-f>] derivative gives an imidazolo fused pyridopyrazine with acetic anhydride (75USP3898216). The oxidative removal of hydrazino groups has been used to give ring-unsubstituted derivatives (79JHC305). 

The pyrazole (420) is formed when the pyrazolidine (418) is heated with chloranil and the intermediate A -pyrazoline (419) (one of the rare A(l)-unsubstituted derivatives) can be isolated (78TL4503). 

Sodium borohydride and 3-isoxazolium salts with a 3-unsubstituted position also give isoxazolines, as do the 3-substituted 5-unsubstituted derivatives. With the latter group, further reduction occurs to the isoxazolidines (74CPB70). 

The treatment of ethyl Af-methyl-5-oxo isoxazoline-4-carboxylate with NaOH generated ethyl Af-methylmonomalonamide. The reaction in the case of 3-unsubstituted derivatives... 

The mixed ortho ester formed from tri(2-chloroethyl) orthoformate (100°, 10 min-2 h, 16% yield) is more stable to acid than is the unsubstituted derivative, but can be cleaved with 80% AcOH (20°, 1 h). ... 

Xanthen-9-ol, TFA, CH2CI2 25°, 30 min. The 2-methoxy analogue can be prepared similarly, and it is cleaved only slightly faster than the unsubstituted derivative. 

In solution and in the solid state, imidazole and its N2-unsubstituted derivatives form large hydrogen-bonded associates 13 (Scheme 8) [76AHC(S1), p. 266 84CHEC-I(5)345,84JPC5882 96CHEC-II(3)77 97JST(415)187]. 

Conformations of 4-oxo-l,6,7,8,9,9n-hexahydro-4//-pyrido[l,2-n]pyrimi-dine-3-carboxylates and -3-carboxamides were studied by semiempirical quantum chemical calculations at the AMI level (97H(45)2175). While 1-methyl-9n-unsubstituted derivatives adopt a cA-fused conformation, 9a-ethoxy-1-methyl derivatives adopt a trans-fu ed one to avoid a serious non-bonding interaction between 9n-ethoxy and 1-methyl groups, which would be present in an alternative cA-fused conformation. 

Vilsmeier-Haack formylation of 2-(4-methyl-l-piperazinyl)-4//-pyrido-[l,2-n]pyrimidin-4-one with a mixture of POCI3 and DMF at 95°C gave a 3-formyl derivative (93FES1225) while ethyl 4-oxo-6,7,8, 9-tetrahydro-4//-pyrido[l,2-n]pyrimidine-2-acetate at 50 °C yielded a 9-dimethylaminomethylene-3-formyl derivative (01MI4). 3-Formyl-2-hydroxy-8-[2-(4-isopropyl-l,3-thiazol-2-yl)-l-ethenyl]-4//-pyrido[l,2-n]pyri-midin-4-one was obtained from the 3-unsubstituted derivative with oxalyl chloride-DMF reagent in CH2CI2 at room temperature for 3h (OlMIPl). 

Treatment of 2-[(4-methoxyphenyl)methyl] derivative of 2,3,6,7-tetra-hydro-l//,5//-pyrido[3,2,l-//]quinazoline-l,3-diones with (NH4)2Ce(N03)g afforded 2-unsubstituted derivatives. A 2-unsubstituted derivative was N-alkylated with 4-methoxybenzyl chloride in DMF in the presence of K2CO3 at 50 °C (01MIP22). 

Heating 3-hydroxymethyl derivative of epimeric 6-methyl-l,3,4,6,7,l l/>-hexahydro-2//-pyrimido[6,l-n]isoquinolin-2-ones 151 resulted in the formation of 3-unsubstituted derivatives 152 by loss of CH2O (97LA1165). 

Difluoro-3-methyl-8-nitro-7-oxo-2,3-dihydro-7//-pyrido[l,2,3- /e]-l, 4-benzoxazine-6-carboxylic acid was obtained from 8-unsubstituted derivative by treatment with KNO3 (99MI56). 

Although theseazepin-2-onesexhibitdeshieldedprotonresonances(<5 = 7.8 8.2), with an ortho coupling for the 5,6-unsubstituted derivative of J5 6 = 10 Hz, an X-ray structural analysis of ethyl 7-(4-bromophenyl)-3-methoxy-2-oxo-6-phenyl-27/-azepine-4-carboxylate reveals a non-planar azepine ring 48 53 3,5-Dihaloazepin-4-ones have been detected recently in the photolysis of 4-azido-2,6-dihalophenols at 12-14 K.286... 

The formation of phthalocyanines can be formally regarded as cyclotetramerization of the appropriate substituted or unsubstituted derivatives of phthalic acid. It should be emphasized that mixtures of structural isomers are obtained if these derivatives are substituted as follows ... 

Substituent effects on the Vax of the colored form in these series are interesting and are dependent on the pyran component. For compound 20, substitutions at position 3, 6, or 8 (or 3, 6, 8 ) affects the X substantially, i.e., the absorption band lies in a wide range 475-609nm. The 7,7 -, 8,8 -, or 10,10 -dinitro-substituted compounds 21 reveal a somewhat hypso-chromic shift, relative to unsubstituted derivative, whereas the bathochromic shift (1(M0 nm) is observed with dinitro substitution at the same position in compound 22. For compound 23, the pronounced shift is also observed with 8-nitro substitution. Many other spectral data are collected in Ref. 1. 

The bromine atom of 4-aryl-2-(4-bromobutyl)-2,3,5,6,7,8-hexahydro-177- ancj -perhydropyrido[l,2-c]pyrimidine-l,3-diones was displaced with 4-substituted piperazines <2002FES959, 2004APH139, 2004PHA99>. Heating 3-hydroxymethyl derivatives of epimeric 6-methyl-l,3,4,6,7,llb-hexahydro-277-pyrimido[6,l-,2]isoquinolin-2-ones 152 resulted in the formation of the 3-unsubstituted derivatives 153 by loss of CH20 (Equation 26) <1997LA1165>. 

The ring cleavage of 3-aryl-2-substituted-2//-azirines by molybdenum hexacarbonyl has been described earlier in regard to the synthesis of pyrroles, pyrazoles and isoxazoles. In contrast to this behavior, analogous reactions of 2-unsubstituted derivatives lead to the formation of mixtures of 2,5-diarylpyrazines (139) and isomeric 3,6- and 1,6-dihydropyrazine derivatives (140,141) (Scheme 163).47,53 It is possible that the pyrazine products are formed by an intermolecular nitrene mechanism akin to the intramolecular processes described earlier (see Scheme 22 in Section IV,A,1). 

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