- Synthesis and Thermolysis of Hydroxyalkene Lactones or Lactams Possessing a Morpholinobicycloalkyl Moiety
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A morpholinobicycloalkyl moiety can be transferred easily to hydroxycumarin (2C), hydroxyquinolone 2D, hydroxypyrone 2E, hydroxypyridone 2F, or tetronic acid (2G) by reaction with the N,O-acetal 1.Thermolysis of the C-alkylation products 3C-3G causes morpholine elimination and formation of alkylidenedihydrofurans 13a or 12d, preferentially in the case of a bicyclohexane- or a -dodecane system.On the other hand, heating the corresponding bicycloheptane- or -octane derivatives 3b, c in most cases effects a ring opening generating the diacyleneamines 4b, c which werehydrolyzed for characterization to give 5 or 6.Additionally, the course of the thermolysis is influenced by the type of the CH acid in 3, thereby increasing CH acidity favours elimination of morpholine.Alkylidenedihydrofurans are obtained stereospecifically as Z isomers 13 from the bicyclic compounds 3a-c and as E isomers 12 from the bicyclododecane derivatives 3d.Lactone or lactam structures 12 and 13 are found exclusively for the alkylidenedihydrofurans isolated from the decomposition of 3C, 3E, 3F, and 3G.The hydroxyquinolone compound 3D gives small amounts of the 4-quinolone derivatives 9Dd or 10Da besides 12Dd or 13Da as main products.The alkylidenedihydrofurans 12 or 13 and 9 or 10 are isomerized quantitatively by acid catalysis into the corresponding furans 14 and 16, respectively.In some cases a (diacylmethylene)cyclopropane 8 as a potential intermediate of the thermolysis can be trapped leading to 18.
- Maischein, Juergen,Vilsmaier, Elmar
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p. 355 - 370
(2007/10/02)
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