A-methoxy

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]. 

The key step in the total synthesis of rhizobitoxine is the Pd-catalyzed exchange reaction of the methyl alkenyl ether moiety in 4 with the functionalized alcohol, although the yield is low[3]. The enol pyruvate 6 (a-ethoxyacrylic acid) is prepared by the reaction of methyl a-methoxyacrylate or a-methoxy-acrylic acid (5) with ethanol catalyzed by PdCl2(PhCN)2 at room temperature in the presence of CuCli and NaH2P04[4],... 

Another version of the o-aminobenzyl anion synthon is obtained by dilithi-ation of A-f-Boc-protected o-alkylanilines. These intermediates are C-acylated by DMF or A"-methoxy-At-melhyl carboxamides, leading to either 3- or 2,3-disubstituted indoles. In this procedure dehydration is not spontaneous but occurs on brief exposure of the cyelization product to acid[4]. Use of CO as the electrophile generates oxindoles. 

Diastereomeric derivathation of a chiral alcohol (111) with an enantiopure compound such as Mosher s reagent [20445-33-4] (a-ttifluoromethyl-a-methoxy-a-phenylacetjichloride) (112) (91) results in two distinct compounds (113) and (114) with nonequivalent chemical shifts in the H-nmr spectmm (92). 

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%. 

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... 

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. 

TiCl3, H2O, It, 1 h, 85% yield.This is an excellent reagent that works when cleavage of a methoxy oxime with chromous ion fails. 

The empirical formula contains five double-bond equivalents. In the H NMR spectrum a doublet signal at Sh = 9.55 stands out. This chemical shift value would fit an aldehyde flinction. Since the only oxygen atom in the empirical formula is thus assigned a place, the methyl signal at Sh = 3.80 does not belong to a methoxy group, but rather to an /f-methyl group. 

The occurrence of nucleophilic participation is also indicated by a rate enhancement relative to the rate of solvolysis of n-butyl p-bromobenzenesulfonate. The solvolysis rates of a series of cu-mefhoxyall l p-bromobenzenesulfontes have been determined. A maximum rate is again observed where participation of a methoxy group via a live-membered ring is possible (see Table 5.20). 

Fig. 10.2. MO diagram for anisole by applicatbn of perturbation for a methoxy substituent.

Accepting Gadamer and Winterfeld s view that this base is a methoxy-chelidonine, von Bruclihausen and Bersch suggested that the methoxyl group was probably at (III, p. 278). 

The authors point out that erythrophleie acid may be a methoxy-derivative of cassaic acid,... 

Anodic oxidation of N-alkyl-N-fluoroalkylanilines m methanol mlroduces a methoxy group into fluonnated alkyls [ 9] (equation 81)... 

The largest shifts in frequency occur for methyl acetate, where the hydrogens in formaldehyde are replaced by a methyl group and a methoxy group, and most strikingly in acetyl chloride, where the hydrogen atom is replaced by a chlorine atom and a methyl group. 

A/,A/-Dimethyiimidazoiidine, 360 A/,A/ -Diaryiimidazoiidine, 360 2,3-Dihydro-1,3-benzothiazoie, 361 Diethylamine Adduct, 361 A/-Methoxy-A/-methyiamine Adduct, 362 o-Carborane, 362... 

Brassard " applied the Conrad-Limpach reaction as an approach to the A-B ring system of Phomazarin. While the overall yield was only 23%, he showed that a methoxy group was an acceptable substituent on enamino-ester 46 and for the subsequent cyclization to quinolone 47. 

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