Methoxy 1 group

Fig. 1. A single step perturbation fails for the mutation of p-methylphenol to p-methoxyphenol because no configuration with a cavity large enough to accommodate the methoxy group is sampled in a simulation of p-methylphenol in water.

Partial rate factors for the nitration of 4-hydroxyquinoline and its derivatives are given in table 10.6. Comparison with the values for quinolinium (table 10.4) show that the introduction of a 4-hydroxy or a 4-methoxy group into the latter activates the 6-position by factors of 3-3 X 10 and 1-6 X 10 , respectively, and the 8-position by factors of 29-5 and 23, respectively. What has been said above makes the significance of partial rate factors which may be calculated for 4-hydroxy-cinnoline uncertain. 

The oxidation of the cyclic enol ether 93 in MeOH affords the methyl ester 95 by hydrolysis of the ketene acetal 94 formed initially by regioselective attack of the methoxy group at the anomeric carbon, rather than the a-alkoxy ketone[35]. Similarly, the double bond of the furan part in khellin (96) is converted ino the ester 98 via the ketene acetal 97[l23],... 

When butadiene is treated with PdCU the l-chloromethyl-7r-allylpalladium complex 336 (X = Cl) is formed by the chloropalladation. In the presence of nucleophiles, the substituted 7r-methallylpalladium complex 336 (X = nucleophile) is formed(296-299]. In this way, the nucleophile can be introduced at the terminal carbon of conjugated diene systems. For example, a methoxy group is introduced at the terminal carbon of 3,7-dimethyl-I,3,6-octatriene to give 337 as expected, whereas myrcene (338) is converted into the tr-allyl complex 339 after the cyclization[288]. 

Methoxythiazole has been prepared by the Williamson reaction. The methoxy group exerts a bathochromic effect on the 233-nm band of the thiazole and shields both C-2H and C-5 H (0.67 and 0.89 ppm) (289). 

In these examples the base name of the benzene derivative determines the carbon at which numbering begins anisole has its methoxy group at C 1 toluene its methyl group... 

This reaction has been used m an imaginative way to determine the ring size of glycosides Once all the free hydroxyl groups of a glycoside have been methylated the glycoside is subjected to acid catalyzed hydrolysis Only the anomeric methoxy group IS hydrolyzed under these conditions—another example of the ease of carbocation for matron at the anomeric position... 

Significant quantities of the diphenoquinone are also produced if the ortho substituents are methoxy groups (36). Phenols with less than two ortho substituents produce branched and colored products from the reactions that occur at the open ortho sites. It is possible to minimize such side reactions in the case of o-cresol oxidation by using a bulky ligand on the copper catalyst to block the open ortho position (38). 

Fig. 8. Basic chemistry of acetoxy-based RTV sihcones. The reactions for curing methoxy-based RTV sihcones are the same in that case, the methoxy group (OCH ) replaces acetoxy (OOCCH ), and methanol (CH OH), rather than acetic acid (CH COOH), is formed.

When camphene reacts with guaiacol (2-methoxyphenol), a mixture of terpenyl phenols is formed. Hydrogenation of the mixture results ia hydrogenolysis of the methoxy group and gives a complex mixture of terpenyl cyclohexanols (eg, 3-(2-isocamphyl) cyclohexanol [70955-71 (45)), which... 

However, moxalactam is highly resistant to a broad spectrum of P-lactamases owiag to the effect of the 7a-methoxy group (194,195). 

The early chemistry leading to these derivatives was originally carried out via the 6a-(methylthio) derivative (17) which was prepared by way of a Schiff s base (39). The 6a-thiomethyl group could then be displaced by various nucleophiles giving rise to 6a-methoxy or other 6a-substituted penicillins. A stereo-specific one-step introduction of a methoxy group at C-6 in penicillins provided a simple entry to 6a-methoxy penicillins (40) in yields ranging from 50—62%. 

After formation of the acylimine (12), methanol adds to the less sterically hindered a-face of the molecule with high selectivity to provide (13). A further direct incorporation of a 6a-methoxy group (41) and subsequendy a 6a-formamido group into penicillin has been achieved using ttiduoromethanesulfonamides of type (14) (42). 

Methylation of avermectins B and B2 leads to the corresponding derivatives of the A series (49). A procedure involving the oxidation of the 5-methoxy group with mercuric acetate and NaBH reduction of the 5-keto-intermediate allows the conversion of the A to the B components (50). The 23-hydroxy group of the "2" components, after selective protection of the other secondary hydroxy groups, is converted to a thionocarbonate, which can be elirninated to give the 22,23-double bond of the "1" components alternatively it can be reduced with tributyltin hydride to the 22,23-dihydro derivatives (= ivermectins) (51). 

Another important use of BCl is as a Ftiedel-Crafts catalyst ia various polymerisation, alkylation, and acylation reactions, and ia other organic syntheses (see Friedel-Crafts reaction). Examples include conversion of cyclophosphasenes to polymers (81,82) polymerisation of olefins such as ethylene (75,83—88) graft polymerisation of vinyl chloride and isobutylene (89) stereospecific polymerisation of propylene (90) copolymerisation of isobutylene and styrene (91,92), and other unsaturated aromatics with maleic anhydride (93) polymerisation of norhornene (94), butadiene (95) preparation of electrically conducting epoxy resins (96), and polymers containing B and N (97) and selective demethylation of methoxy groups ortho to OH groups (98). 

Goal Constitution. Chemical composition studies (35,36) indicate that brown coals have a relatively high oxygen content. About two-thirds of the oxygen is bonded carboxyl, acetylatable hydroxyl, and methoxy groups. Additionally, unlike in bituminous coals, some alcohoHc hydroxyl groups are beheved to exist. 

The synthesis (60) and potent antitussive activity (61) of dimemorfan [36309-01-0] (41), D-3-methyl-/V-methylmorphinan, have been reported. This compound, prepared by a modification of the Grewe process, differs from dextromethorphan only by having a methyl group, rather than a methoxy group, in the 3 position. 

Pyridazine 1-oxides substituted at position 3 or positions 3 and 6 afford the corresponding 5-nitro derivatives. A methyl group at position 6 (a with respect to the iV-oxide group) is frequently converted into the cyano group, and a methoxy group at position 6 is demethy-lated by benzoyl chloride/silver nitrate. For example, 3-substituted 6-methylpyridazine 1-oxides give the 5-nitro derivatives (96) and the 6-cyano-5-nitro derivatives (97), whereas... 

When alkoxypyridazine 1-oxides are heated alone or in the presence of p-toluenesulfonic acid the methyl group migrates from the methoxy group to the A-oxide group. In this manner, 4-methoxypyridazine 1-oxide rearranges to l-methoxypyridazin-4(l//)-one, 5-methoxypyridazine 1-oxide to 2-methylpyridazin-5(2//)-one 1-oxide and substituted 3,6-dimethoxypyridazine 1-oxides to l,3-dimethoxypyridazin-6(l//)-ones. 

There are several alkaloids in the structure of which are both quinazoline and indole nuclei. Evodiamine (1001 R = H) and rutaecarpine (1002) were both isolated from the seeds of Evodia rutaecarpa about 1916 and synthesized in 1927. They were found subsequently to occur also in Xanthoxylum rhetsa, which in addition yielded rhetsinine (1001 R = OH) (59T(7)257). The plant Hortia arborea afforded two more related alkaloids, hor-tiacine and hortiamine, each characterized by a methoxy group in the benzene ring of the indole portion (60JA5187). 

It would appear that this type of addition may not be confined to the addition of NH2 in liquid ammonia, since it has been observed that treatment of 2-chloro-3-dichloromethyl-pyrazine with an excess of methoxide results in the introduction of a methoxy group into the 6-position of the pyrazine ring (Scheme 9) (68TL5931). This reaction is best rationalized in terms of addition of the methoxide ion at the 6-position, followed by loss of chloride ion from the dichloromethyl side chain. 

Methoxy groups undergo alkoxy exchange with potassium hydroxide in alcohols. 

Where an N-methoxy group is present, as in l-methyl-3-methoxybenzimidazole, elimination of MeOH can give an aromatic product. 

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