Electrochemical Syntheses. The Methoxylation of Dimethoxybenzenes to Quinone Ketals and the Ring Fission of 1,2-Dimethoxybenzene to Hexamethyl cis,cis-Orthomuconate

Abstract

COMMUNICATIONS TO THE EDITOR 2525 change rate in basic solutions, proceeding solely via the attack of water on the neutral molecule, therefore is markedly slower. Further work on these and related compounds is in progress.

Enantioselective Synthesis of Natural Polyoxygenated Cyclohexanes and Cyclohexenes from [(p‐Tolylsulfinyl)methyl]‐p‐quinols

“…The enantiomerically pure 4-hydroxy-4-[(p-tolylsulfinyl)methyl]cyclohexa-2,5-dienones (SR)-13 [31] and (SS)-13 (Scheme 2) [12] necessary to synthesize the two enantiomers of dihydroepiepoformin (5) and (+)-gabosine O (6) were obtained, as reported previously, by treatment of the lithium anions derived from (SR)- [32] or (SS)-methyl p-tolyl sulfoxide (12) with p-benzoquinone dimethyl monoketal (11), [33] followed by hydrolysis of the intermediate acetal with oxalic acid, in 76 and 78 % overall yields, respectively.…”

Asymmetric Synthesis of Rubiginones A2 and C2 and Their 11‐Methoxy Regioisomers

“…The synthesis of enantiopure diene 4 began with 3,3,6,6-tetramethoxy-1,4-cyclohexadiene (10), [23] which was subjected to a controlled monohydrolysis with a mixture of acetone/ water 10:1 affording the dimethyl monoketal of p-benzoquinone (11) [24] in 88 % yield (Scheme 2). (SS)-[(p-Tolylsulfinyl)methyl]-p-quinol (9) was synthesized following the procedure reported for the (SR)-enantiomer, [25] by reaction of 4,4-dimethoxy-2,5-cyclohexadienone (11) with the lithium anion derived from (SS)-methyl-p-tolylsulfoxide 12, [26] followed by ketal hydrolysis with aqueous oxalic acid, in 76 % overall yield.…”

Electrochemical Fission of Vicinal Diketals to Orthoesters

“…Orrhobenzoate (3) A solution of 4.8 g of a,a'-dimethoxystilbene (1) (3) in 250 ml of methanol containing 2.5 g of potassium hydroxide was electrolyzed for I h by passing a 3 A current at 12 V while stirring and cooling to 10-15". A platinum anode (total surface area of 160 cm2) and nickel cathode (total surface area of 240 cm2) were used as previously described (1,2).…”

“…A platinum anode (total surface area of 160 cm2) and nickel cathode (total surface area of 240 cm2) were used as previously described (1,2). The anodic current density was of the order of 0.03 A/cmZ.…”

“…During thecourse of our studies on theelectrochemical synthesis of benzoquinone ketals, it was observed that o-benzoquinone tetramethyl ketal possessed the remarkable ability to suffer anodic cleavage in alkaline methanol to the corresponding hexamethyl cis,cis-orthomuconate (1). Because of the unprecedented nature of the reaction, the question arose as to whether this anodic cleavage is substrate specific or applicable to other types of vicinal diketals.…”