Modification of substituents

Substituent Product (reagent) Substituent Product (reagent) 

2-CO2H CONH2 (i, ClC02Et ii, NHj) 3-CH2OH CH2OCOR (RCOCl) 

2-CONH2 CH2NH2 (L1A1H4) 2-COAr - CHOHAr (L1A1H4) 

2-C02Me CONHNH2 NH2NH2, EtOH,2-CH2CH2Br room temp.) CH2CH2OH (AgjO, H2O) 

2-C02Me CO2H (OH, H2O) 2-CH2CH2Br CH2CH2NH2 (Gabriel synth.) 

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In addition to the discussed cyclotetramerizations, direct metallation of the metal-free ligands or metal exchange of a labile metal ion or ions for one held more robustly, the desired complexes may be prepared by the direct substitution, exchange or modification of substituents on preformed phthalocyanine derivatives. However, a review of works carried out on these types of transformations lies out of the scope of this chapter. 

Modification of Substituents and Functional Groups of Cyclic Nitronates At an ambient temperature, four-membered cyclic nitronate containing the chloronitromethyl group at the C-3 atom is gradually transformed into the corresponding acid chloride even under solvent-free conditions, and treatment of the latter with aqueous ammonia affords amide (168) (Scheme 3.119, Eq. 1). 

A large group of reactions leading to modifications of substituents in cyclic nitroso acetals (66, 152, 159, 160, 190, 214, 215, 367, 404, 405) is not considered because, in our opinion, this aspect of chemistry of nitroso acetals, is beyond the scope of the present section. 

Transformation Between Phosphonio-Phospholides by Modification of Substituents... 

Similarly, for die process shown below, die oxidation state of C-l remains at — 1 throughout die sequence tiius die overall sequence involves no change in oxidation level at C-l, nor does either step. Modifications of substituents and substitution of one electronegative group for another are generally not redox processes. 

Progress in the chemistry of l,3-thiazin-4-ones is mainly attributable to their applications in the pharmaceutical area. In the search for new drugs, the most intensive investigation has focused on the modification of substituents in the thiazinone ring and in the syntheses of thiazinones fused with heterocycles. 

All the reactions reported in this section deal with modification of substituents of dioxocins, analogues of the natural antimalarial agent yingzhaosu A, possessing antimalarial activity or utilized in the total synthesis of the natural product. 

Preussomerin I 697 and ( )-preussomerin G 698 were obtained from 620 with a five- and six-steps sequence in 15% and 12% overall yield, respectively, through modifications of substituents of the dioxocin ring. Thus, attack of lithium methoxide from the less hindered face of the enone 620, followed by protection of the phenolic oxygen as its methyl ether provided the methoxy adduct 692. The ketone 693 was obtained through a benzylic bromination-solvolysis-oxidation protocol, which required only a single purification. The C(2)-C(3) olefin was introduced by selective silylation of the C-l carbonyl of diketone 693 and oxidation of the silyl enol ether with Pd(OAc)2. Enone... 

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