Ketones ethinylation

If homolytic reaction conditions (heat and nonpolar solvents) can be avoided and if the reaction is conducted in the presence of a weak base, lead tetraacetate is an efficient oxidant for the conversion of primary and secondary alcohols to aldehydes and ketones. The yield of product is in many cases better than that obtained by oxidation with chromium trioxide. The reaction in pyridine is moderately slow the intial red pyridine complex turns to a yellow solution as the reaction progresses, the color change thus serving as an indicator. The method is surprisingly mild and free of side reactions. Thus 17a-ethinyl-17jS-hydroxy steroids are not attacked and 5a-hydroxy-3-ket-ones are not dehydrated. 

Bicyclo 4.1.0]heptan 7-Trimethyl-silylcarbonyl- E17b, 1393 (7-Br/7-SiR3 — 7-H/7-CO—SiR3) Cyclohexan trans-2-Hydroxy-1-(trimethylsilyl-ethinyl)- E19d, 146 (sp-CH - C - Li/Oxiran) Cyclopenten 2-Ethyl-4-methylen-l-trimethylsilyl- E17c, 2251 (Methylen-cyclo propan + In) Ethen l-(l-Cyclohexenyl)- -trimethylsilyloxy- E1S/1, 441 (Keton 4- RjSi—O —S02 —R) Furan 2-Methyl-5-propyl-3-trimethylsilyl- E18, 674 (In-Hydromagnesier./+ R —CN)... 

Three important processes have evolved from Reppe s work. Vinylation, the formation of vinyl derivatives by reaction of such compounds as acids, glycols, and alcohols with acetylene, produces the important vinyl esters and vinyl ethers. Ethinylation is defined as the reaction of acetylene with the carbon atom of a reactant without loss of the triple bond. A major application of the ethinylation reaction is to aldehydes and ketones to give alkynols and alkyndiols—e.g., the reaction of acetylene with formaldehyde to give propargyl alcohol and butyn-2-diol-l,4. Carboxylation (also referred to as carbonylation), the reaction of acetylene with carbon monoxide in the presence of metal carbonyls, has been applied to the production of acrylic acid, acrylates, and hydroquinone. 

For over a decade, hormonal activity of any consequence was thought to be limited to steroids containing a A4-3-keto group. A recent development of much interest, therefore, is the removal of the 3-ketone from VIII (R = X = H) via thioketal formation and reduction with sodium in liquid ammonia. Subsequent oxidation and ethinylation afforded the 3-deoxy derivatives of XIII and XV (20). The latter, lynestrenol, possesses marked progestational properties. High potency was also found when the ketone (XV, R = X = H) was reduced... 

Hydroxymethylene ketones, the corresponding enol ethers, and ethinyl ketones can be used in the Claisen synthesis. 

Lithium acetylide reacts very smoothly with ketones. For example, it combines rapidly with 2-norbomanone (bicyclo[2.2.1]heptan-2-one) to give 1-exo-ethynyl-2-e (io-norbomanol. If camphor is the substrate the ethinyl groups enters on the endo face. The addition of acetylene onto ketones can even be brought about by catalytic amounts of potassium ter/-butoxide. ... 

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