REACTIONS OF SUBSTITUENTS

Reactions of substituents not directly attached to the heterocyclic ring... 

In benz- and phenyl-azolones, electrophilic substitution often occurs in the benzene ring such reactions are considered as reactions of substituents (see Sections 4.02.3.2.1 and 4.02.3.4.1). 

Reactions of Substituents on Thiirane Rings S.06.3.9.1 Reactions on carbon... 

Reaction of Substituents Attached to Ring Carbon Atoms. 276... 

No information is available regarding the reactions of substituents attached to ring carbon atoms. 

This subsection contains some more or less general reactions of substituents of 5-5, 5-6, and 6-6 bicyclic compounds containing two ring-junction nitrogen atoms described in the literature since the CHEC-II(1996) publication <1996CHEC-II(8)747>. 

The reactions of substituents on ring nitrogen atoms in 1,3,4-oxadiazolium cations 2 and exocyclically conjugated mesoionic 1,3,4-oxadiazoles 3 are uncommon. Similar reactions of compounds 4 and 5 were reported occasionally. Biphenylmethylation of 2-trifluoroacetamido-l,3-4-oxadiazole 105 occurred regioselectively (Scheme 23), affording only the 2-acylimino derivative instead of the expected product 106 <1997H(44)133>. 

CHEC-II(1996) <1996CHEC-II(8)345> covered a range of reactions of substituents, including hydrolyses of esters to carboxylic acids and geminal dihalides to aldehydes, reduction of aldehydes and halogens directly attached to the ring, O-methylation with diazomethane, and reduction of nitroso compounds. A selection of reactions which have... 

Reactions of substituents attached to the ring carbon atoms have only been reported sparingly. The results are shown in Scheme 7. 

A great number of transformations of substituents - mostly by well-established routine methods - have been applied. In this section, those reactions are reviewed where the atom of the substituent attaching to the ring carbon atom of the heterocycle is changed in the course of the transformation, and could not be classified into the previous sections. Reactions of substituent where the transformation occurs in the side chain are summarized in Section 11.17.5.7. 

Two photochemically induced reactions of substituents have been reported which require the participation of the triazole ring. Irradiation of 3-(l-methyltriazol-4-yl)acraldehyde in methanol gave the saturated ester 23 in high yield, whereas the corresponding quaternary salt 24... 

Few reports describe reactions of substituents at the benzene ring of benzotriazoles. The facile deprotonation of the methyl group in N-Boc-7-methyl-1-aminobenzotriazole (403) with butyllithium followed by reactions with electrophiles gives substituted products (404) (Scheme 78). The electrophile can be an alkyl halide, an aldehyde or a ketone, and the Boc group is removed by brief exposure to CF3CO2H in CH2CI2 <93TL6935>. 1-Acetylbenzotriazole (405) is hydrolyzed to form 3-(177-5-hydroxybenzotriazol-6-yl)propionic acid (406), which is then converted (Scheme 79) to... 

Numerous publications have been devoted to the reactions of substituents attached to the nitrogen atoms of 1,2,3-triazoles, and particularly of benzotriazoles. Several comprehensive reviews have appeared <91X2683, 94M1 401-01, 94S445>. 

Reactions of substituents with an ct-amino or ct-inuno group... 

---