Cyclohexanone ethylene ketal

BFj-etherate added to a soln. of cyclohexanone ethylene ketal in methylene chloride at —78° under N2, the mixture treated dropwise with a soln. of l,2-bis(trimethyl-siloxy)cyclopentene in the same solvent, and the stirred mixture allowed to warm to room temp, overnight product. Y 89%. The method allows efficient preparation of 2,2-dialkylated 1,3-cyclohexanediones and is a useful alternative to routine double alkylation procedures. F.e. and from dialkyl ketals s. Y.-J. Wu, D.J. Burnell, Tetrahedron Letters 30, 1021 (1989). 

Cyclohexanone ethylene ketal treated at room temp, with trityl fluoroborate in methylene chloride cyclohexanone. Y 80%. - Similarly during 4 hrs. 0,0-Isopropylidenecholestane-2j, 3j -diol 3j -hydroxydiolestan-2-one. Y 79%. F. e. s. D. H. R. Barton et al., Chem. Commun. 1971, 861 removal of protective groups by hydroxide transfer under mild and neutral conditions s. a. Chem. Commun. 1971, 1109 Soc. Perkin I 1972, 542. 

Synthesis of cyclohexanone ethylene ketal from cyclohexanone and ethylene glycol 84.3 [203]... 

Yang, S. Wu, Yu Sun, J. Catalytic Synthesis of Cyclohexanone Ethylene Ketal by Rare Earth Solid Superacid S04 /Ti02-La203. Chem. React. Eng. Technol. 2003, 19(4), 311-315. 

XXII-A is destabilized in the corresponding ketal derivative XXVI. An equatorial but not axial group at C-14 would be destabilized by the adjacent ethylene ketal ring. This phenomenon has been confirmed in a simpler system and provides an interesting method of obtaining the axial isomer from the equatorial in a-substituted cyclohexanones (19). The remaining possible ethylene ketals, mono- and bisketals, of the acetoxy diketones XXI-A and XXII-A, were prepared as part of this study 12). 

I whereupon 1 mole of Hg is I absorbed during 0.5 hr. -> 2-hydroxy-3-cyclohexanone-l-acetic acid ethylene ketal... 

Cyclohexanone (0.52 g, 5.3 mmol) is added, under a nitrogen atmosphere, to a mixture of dry ethylene glycol (3 mb, 54 mmol) and dry methanol (20 mb). Tri-methylchlorosilane 14 (1.4 mb, 11 mmol) is added and the mixture stirred for 16 h at room temperature. The mixture is neutralized to pH 6 by addition of a 5% solution of sodium methoxide in methanol and the solvent is removed under reduced pressure. The residue is dissolved in 20 mb ether and filtered through 5 g silica gel, which is then washed with 2x10 mb ether. The combined ether eluates are evaporated and the crude residue submitted to flash chromatography on silica gel with ethyl acetate-hexane (1 10) to give 0.63 g (83%) cyclohexanoneethylene ketal 392 [28] (Scheme 5.87). 

Scheme 8.52. The formation of, first, a hemiketal and, second, a (cyclic) ketal as a result of the acid-catalyzed addition of 1,2-dihydroxyethane (ethylene glycol, HOCH2CH2OH) to cyclohexanone.

The formation of hemiketals and ketals from alcohols and ketones is exactly analogous (with somewhat more difficulty as ketones are generally less reactive than aldehydes Chapter 9). In the reaction of a ketone, such as cyclohexanone (Table 8.6, item 12) with a 1,2-diol, such as 1,2-dihydroxyethane (ethylene glycol [HOCH2CH2OH]) (Scheme 8.52), the second equivalent of alcohol is part of the initial alcohol substrate and the cyclic product results. 

Similarly, as shown in Scheme 9.62 (a repetition of what was previously seen as Scheme 8.52),the reaction of 1,2-dihydroxyethane (ethylene glycol [HOCH2CH2OH]) with cyclohexanone (again with acid catalysis) produces, first, the hemiacetal and then, following a second proton transfer, loss of water and addition of the second hydroxyl of 1,2-dihydroxyethane (ethylene glycol [HOCH2CH2OH]) to produce the corresponding cyclic ketal. 

Many chemical reactions are catalyzed by acids but on a large-scale can generate significant amoimts of acid waste, which requires neutralization and/ or disposal. In principle, CO dissolved in water is mildly acidic, due to formation of carbonic acid and should be capable of catalyzing a range of reactions. Simple pressure release at the end of the reaction brings the pH back to levels, which require minimal neutralization. Hydrolysis of ketal to cyclohexanone and ethylene glycol and epoxides to diols are a few examples where CO in presence of water have been used as a catalyst [322]. 

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