Diisobutyl ketone enamine from

As with imines, enamine formation may be achieved using azeotropic distillation,219 or with the aid of molecular sieves. The procedure described in Expt 5.201 for the preparation of the enamine from morpholine and diisobutyl ketone utilises titanium(iv) chloride as a catalyst and water scavenger.220... 

Fig. 14.2 Variation in the conditions affording the maximum yield in the synthesis of morpholine enamines from a series of carbonyl compounds (1) methyl isopropyl ketone, (2) pinacolone, (3) methyl isobutyl ketone, (4) methyl neopentyl ketone, (5) diethyl ketone, (6) diisopropyl ketone, (7) ethyl isobutyl ketone, (8) diisobutyl ketone, (9) isobutyraldehyde,...

The Stork-Dolfini synthesis of the amino ketone 458 requires some 11 steps clearly, this is an area for improvement. One method used has been that of methyl vinyl ketone annelation (237). This procedure had been used previously in a synthesis of mesembrine (238) involving 2- -rolines. Stevens hoped to extend this technique to endocyclic enamines to give compounds in the octahydroquinolone series. 3-Ethylpiperid-2-one (549) was prepared from the y-lactone 550 according to standard procedures (239). N-Benzylation followed by reduction with diisobutyl-aluminum hydride (DIBAL) gave enamine 473. Addition of the enamine to methyl vinyl ketone (551) gave an almost quantitative yield of a hydroquinoline 552, which could be readily debenzylated to the known amino ketone 458. As with the Stork method of synthesis, this route to the Aspidosperma nucleus is efficient for the parent compounds but appears to lack the potential for diversification required to synthesize the more complex alkaloids such as vindoline (101) or even tabersonine (28). 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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