Pinacolone, reaction with acetylenes

Potassium or lithium derivatives of ethyl acetate, dimethyl acetamide, acetonitrile, acetophenone, pinacolone and (trimethylsilyl)acetylene are known to undergo conjugate addition to 3-(t-butyldimethylsiloxy)-1 -cyclohexenyl t-butyl sulfone 328. The resulting a-sulfonyl carbanions 329 can be trapped stereospecifically by electrophiles such as water and methyl iodide417. When the nucleophile was an sp3-hybridized primary anion (Nu = CH2Y), the resulting product was mainly 330, while in the reaction with (trimethylsilyl)acetylide anion the main product was 331. 

It has been found that 3-azapyrylium salts 57 and 58 are obtained in reactions of pinacolone as well as vinyl chlorides 59 with N-acylnitrilium salt 56 (91ZOR2479 92ZOR2577). The acylation of vinyl chlorides 59 in benzonitrile also leads to salts 60 (91ZOR1986). The same salts 55 are formed as intermediates by acylation of acetylenes in the presence of nitriles (88ZOR1605). Vinyl chlorides and acetylenes are both direct derivatives of carbonyl compounds with the same oxidation level (72MI2 85KGS1443). 

Nafion-H is a convenient acid catalyst for pinacolone rearrangements. Hydration of acetylenes can be conducted with Nafion-H impregnated with mercury(II) ions. Diels-Alder catalyst. This protic resin catalyzes Diels-Alder reactions, but longer reaction times are needed than in reactions catalyzed by Lewis acids. The reactions are generally conducted in refluxing benzene or chloroform. In the case of dienes that polymerize readily, the reaction is conducted at room temperature for 1-2 days.°... 

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See also in sourсe #XX -- [ ]

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