Addition von Aldehyden an aktivierte Doppelbindungen,XXXIV1). Addition von Aldehyden an cyclische α-Methylenketone

Addition of Aldehydes to Activated Double Bonds, XXXIV¹⁾. Addition of Aldehydes to Cyclic α-Methylene Ketones The thiazolium salt-catalyzed addition of aldehydes to the cyclic α-methylene ketones 3, 4, 7, 8, 48 , and 49 leads to γ-diketones 9 – 22, 50 – 53 ; some of them were converted into unsaturated ketones 23 – 28 , pyrroles 29 – 34, 37 – 43 , and furans 35, 36, 44 – 46 . The α-methylene ketones were synthesized by retro Diels-Alder reaction of the corresponding norbornene compounds 1, 2, 5, 6, 47 .