bottleneck (Newbee) 08-22-02 12:48 No 347768				1,4-Dimethoxy in two steps from benzene (Rated as: excellent)	Bookmark
						Hi, p-Benzoquinone tetramethyl diketal can be made by anodic oxidation of benzene or anisole in methanol. 1,4-dimethoxybenzene can be made by reduction of the diketal in slightly acidic medium, while 2,5-dimethoxychlorobenzene is made by chlorination by HCl in aprotic solvent. There seems to be some confusion in the patents as to what the product of the hydrogenation of the diketal in basic medium is, but otherwise it seems straightforward enough. Wonder if starting with phenethylamine, any 2C-H could formed in a similar reaction. In fact, if one used a para-substituted phenethylamine, I think the 2C-something has to be the result, since this kind of electrolytic oxidation apparantly always produces para-substituents. ------- United States Patent 4,046,652 - Process for preparing p-benzoquinone diketals p-Benzoquinone tetramethyl diketal can be formed by anodic oxidation of benzene, and suggests alkali nitrates, perchlorates and fluorides, etc. as conductive salts to facilitate the electrolytic oxidation of unsubstituted benzene. This gives quinone upon acid hydrolysis. United States Patent 4,057,586 - Process for the manufacture of hydroquinone dimethyl ethers p-Benzoquinone tetramethyl diketal can be formed by anodic oxidation of benzene, and suggests alkali nitrates, perchlorates and fluorides, etc. as conductive salts to facilitate the electrolytic oxidation of unsubstituted benzene. 1,4-Dimethoxybenzene is prepared from p-benzoquinone tetramethyl diketal by catalytic hydrogenation in the presence of propionic acid. United States Patent 4,066,708 - Process for preparing chlorinated hydroquinone dimethyl ethers p-Benzoquinone tetramethyl diketal gives 2,5-dimethoxychlorobenzene on treatment with HCl in aprotic solvent United States Patent 4,082,809 - P-Benzoquinone diketals p-Benzoquinone tetramethyl diketal can be formed by anodic oxidation of benzene, and suggestses alkali nitrates, perchlorates and fluorides as conductive salts to facilitate the electrolytic oxidation of unsubstituted benzene. 1,4-Dimethoxybenzene is prepared from p-benzoquinone tetramethyl diketal by catalytic hydrogenation in the presence of propionic acid. Non-para-substituted anisols give substituted para-benzoquinones. United States Patent 4,160,109 - Cyclohexene-(1)-dione-(3,6)-tetraalkyldiketals and process Cyclohexene-(1)-dione-(3,6)-tetramethyl diketal is formed upon the catalytic hydrogenation of p-benzoquinone tetramethyl diketal in a basic medium. Upon acid hydrolysis, this yields 1,4-dimethoxybenzene. United States Patent 4,161,614 - Process for the preparation of cyclohexane dione-(1,4)-tetramethyl diketal Cyclohexanedione-(1,4)-tetramethyl diketal is formed upon the catalytic hydrogenation of p-benzoquinone tetramethyl diketal in a basic medium. Upon acid hydrolysis, this yields cyclohexanedione-(1,4). United States Patent 4,203,811 - Process for the manufacture of p-benzoquinone-diketals p-Benzoquinone tetramethyl diketal can be formed by anodic oxidation of benzene, and suggests alkali fluorides as conductive salts to facilitate the electrolytic oxidation of unsubstituted benzene. 1,4-Dimethoxybenzene is prepared from p-benzoquinone tetramethyl diketal by catalytic hydrogenation in the presence of propionic acid. United States Patent 4,204,076 - Hydroquinone dimethyl ether p-Benzoquinone tetramethyl diketal gives cyclohexanedione-(1,4)-tetramethyl diketal on catalytic hydrogenation in a basic medium, which can be further catalytically dehydrogenatied to form 1,4-dimethoxybenzene.