2-Methoxy-5- benzenesulfonyl chloride

The O-alkyl derivatives of those A-oxides, which exist partly or entirely as (V-hydroxy tautomers, may be made by primary synthesis (as above) or by alkylation. Thus, 5,5-diethyl-1-hydroxybarbituric acid (936 R = H) with methyl iodide/sodium ethoxide gives the 1-methoxy derivative (936 R = Me) or with benzenesulfonyl chloride/ethoxide it gives the alkylated derivative (936 R = PhS02) (78AJC2517). 

Amino groups can also be derivatized using acyl chlorides that form amides. A number of suitable acyl chlorides including p-chloro-, p-methoxy-, p-nitroben-zoyl-, p-tolyl-, and p-nitro-benzenesulfonyl chloride have been successfully used for sensitive UV-Vis derivatization of nonabsorbing amine compounds (231). Among all those amide derivatives, p-methoxybenzamides appear more attractive because they exhibit high molar absorptivity at the convenient analytical wavelength of 254 nm. After derivatization in tetrahydrofuran-sodium hydroxide solu-... 

Both 2-methylpyrazine 1- and 4-oxides (625) (obtained by oxidation of 2-methyl-pyrazine with peroxyacetic acid) on treatment with phosphoryl chloride have been claimed to give 2-chloro-3-methylpyrazine(626)but the 2-methylpyrazine-4-oxide used is now known to have been a mixture of the 1- and 4-isomers (734). More recently other workers (735, 736) have claimed that the mixed 2-methylpyrazine 7V-oxides with phosphoryl chloride gave a mixture of 2-chloro-3-, -5-, and -6-methylpyrazine but Nakel and Haynes (686) have shown that 2-methylpyrazine 1-oxide with phosphoryl chloride followed by sodium methoxide gave 2-methoxy-3-methylpyrazine and 6-methoxy-2-methylpyrazine, and 2-methylpyrazine 4-oxide (3-methylpyrazine 1-oxide) similarly treated gave only 2-methoxy-6-methylpyrazine. 3-Trifluoromethylpyrazine 1-oxide with benzenesulfonyl chloride at 1(X)° has been shown to give 2-chloro-6-trifluoromethylpyrazine (44%) (759). 

An initial effort to compare the activity for various substituents on the phenyl ring was accomplished by preparing sulfonamides from commercially available ortho-substituted benzenesulfonyl chlorides. The in vivo and in vitro activity for the ortho-substituted sulfonamides is summarized in Table III. With the exception of the nitro substitution (50), these molecules have good activity on broadleaf weeds. However, only the methoxy (46), trifluoromethoxy (47), and methyl ester (48) have good levels of activity on grass weeds. Additionally, all of these sulfonamides are very injurious to rice, even those with weak levels of overall grass activity. 

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