120254-92-4Relevant academic research and scientific papers
Efficient Syntheses of Vinyl Ethers of Spiroquinol Ketals and Their High-Yield Photochemical Oxygen-to-Carbon -Shift to Spiro-Fused 2,5-Cyclohexadienones
Swenton, John S.,Callinan, Andrew,Wang, Shaopeng
, p. 78 - 85 (2007/10/02)
An efficient route to spiroquinol vinyl ethers involves addition of a 1-lithio-2-(trimethylsilyl)acetylene-substituted benzene to the monoethyleneketal of benzoquinone followed by desilylation/cyclization of the resulting product to give vinyl ethers of spiroquinol ketals.A high-yield photochemical conversion of these vinyl ethers of spiroquinol ketals to ketals of spiro-fused 2,5-cyclohexadienones has been developed.A complication in some of these photochemical reactions is formation of secondary products from light absorbed by the product, spiro dienone ketals.This has been solved by conducting the reaction in the presence of piper ylene, which quenches the triplet-state chemistry of the product spiro dienone ketal without altering the singlet excited-state chemistry of the quinol ketal vinyl ether.The quantum yield for the photochemical -shift reaction in a methyl-substituted vinyl ether is 0.4.Finally, irradiation of quinol spiro vinyl ethers was also observed to give spiro dienones in good yields.Although the spiro dienone is absorbing light in competition with starting quinol vinyl ether in this system, a high yield of product was obtained.The unexpected photochemical stability of these spiro dienones is discussed.The chemistry reported herein establishes an efficient high-yield route to spiro-fused 2,5-cyclohexadienones and their ketals under very mild conditions.
Spiro-Fused 2,5-Cyclohexadienones from the Thermal 1,3-Alkyl Migrations of Quinol Vinyl Ethers. A Strategy for Conversion of a Carbonyl Carbon to a Quaternary Carbon
Wang, Shaopeng,Morrow, Gary W.,Swenton, John S.
, p. 5364 - 5371 (2007/10/02)
Reaction of p-benzoquinone monoketals with 2-lithio derivatives of acetophenone and propiophenone dimethyl ketals results in organolithium addition to the carbonyl group of the quinone monoketal to afford the ketals of 4-aryl-4-hydroxy-1,5-cyclohexadienones.Reaction of these products with aqueous acid results in hydrolysis of 2,5-cyclohexadienone ketal and intramolecular mixed ketal formation between 4-hydroxyl group and the 2-substituted acetyl or propionyl side chain of the aromatic ring.Conversion of this cyclic ketal to the vinyl ether by loss of methanol affords the quinol ether derivatives for thermolysis.Variants of this chemistry were used to prepare a number of spiro-fused vinyl ethers of the p-quinols.At 130-170 deg C these molecules undergo high-yield conversion of the vinyl ether moiety to a ketone, affording spiro-fused 4,4-disubstituted 2,5-cyclohexadienones.Rates have been measured for several of these formal -shifts, and a ρ value of -0.87 was calculated for rearrangement of compounds having aryl substituents on the vinyl ether double bond.This chemistry establishes a high-yield strategy for conversion of p-benzoquinone monoketals, 4,4-dialkoxy-2,5-cyclohexadienones, to spiro-fused 2,5-cyclohexadienones.
SPIRODIENONES VIA A THERMAL UNCATALYZED -OXYGEN-TO-CARBON MIGRATION
Morrow, Gary W.,Wang, Shaopeng,Swenton, John S.
, p. 3441 - 3444 (2007/10/02)
Exocyclic vinyl ethers derived from p-quinols, readily avaiable from aryllithium addition to quinone monoketals, undergo high-yield thermal -oxygen-to-carbon migration, yielding spirodienones.
