Ortho reaction with reagent

The reaction has been applied to nonheterocyclic aromatic compounds Benzene, naphthalene, and phenanthrene have been alkylated with alkyllithium reagents, though the usual reaction with these reagents is 12-20, and Grignard reagents have been used to alkylate naphthalene. The addition-elimination mechanism apparently applies in these cases too. A protected form of benzaldehyde (protected as the benzyl imine) has been similarly alkylated at the ortho position with butyl-lithium. ... 

The latter reagent also methylates certain heterocyclic compounds (e.g., quinoline) and certain fused aromatic compounds (e.g., anthracene, phenanthrene). The reactions with the sulfur carbanions are especially useful, since none of these substrates can be methylated by the Friedel-Crafts procedure (11-12). It has been reported that aromatic nitro compounds can also be alkylated, not only with methyl but with other alkyl and substituted alkyl groups as well, in ortho and para positions, by treatment with an alkyllithium compound (or, with lower yields, a Grignard reagent), followed by an oxidizing agent such as Bra or DDQ (P- 1511). 

Ortho-esters at position 1,2- of sugars are more easily prepared than the corresponding acetals as an exchange of both functional groups is possible, 1,2-O-alkylidene derivatives can be prepared by the reaction of these ortho-esters with the appropriate carbonyl reagent in strictly anhydrous conditons and in the presence of an acid [87]. 

OPA (ortho-phthalaldehyde) Aex = 340 nm, Aem = 455 nm. Derivatives are not stable (minutes). OPA is best used as a postcolumn derivatizing reagent. Precolumn use necessitates well-controlled and automated (mechanized) handling of the sample/reagents to ensure uniformity of time elapsed from reaction to injection. It reacts with primary amines only. Proline can be detected only if first converted to primary amine by oxidative reagents like chloramine T or sodium hypochlorite. Conversely, the concomitant reaction with OPA followed by FMOC obviates this problem and is the basis of the AminoQuant system marketed by Hewlett-Packard... 

Povidone-iodine gives a positive reaction with an ortho-toluidine reagent used to detect blood in the urine, for example Hematest reagent tablets or dipsticks (SEDA-11, 488 47). 

Protection of the amino group by acetylation, as in acetanilide, therefore usually permits monosubstitution reactions with appropriate electrophilic reagents to proceed smoothly. Thus with bromine, p-bromoacetanilide is the main product the small quantity of the ortho isomer simultaneously formed can be easily eliminated by recrystallisation (Expt 6.67) hydrolysis of p-bromoacetanilide gives p-bromoaniline. Nitration leads similarly to p-nitroacetanilide which can be hydrolysed to p-nitroaniline (Expt 6.68). 

This method cannot be applied to polynitro amines, since these are so weakly basic that they can be diazotised only under special conditions in strongly acidic media (Section 6.7.1, p. 922). In such cases use may be made of the susceptibility to nucleophilic displacement of halogen when activated by ortho and para nitro groups. Thus the valuable reagent 2,4-dinitrophenylhydrazine (Expt 6.93) is readily prepared by reacting l-chloro-2,4-dinitrobenzene with hydrazine. Reaction with ammonia similarly gives 2,4-dinitroaniline (cognate preparation in Expt 6.93). 

The reaction gives a mixture of the ortho- 53 and para- 54 products. The ortho -compound is converted into saccharine by reaction with ammonia and oxidation and the para-compound toluene-p-sulfonyl chloride 54, or tosyl chloride, is sold as a reagent for converting alcohols into leaving groups. 

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