Tandem conjugate addition-α-alkylation of unsaturated amides. Synthesis of 1-aryltetralin lignans

MPANGO, G. B.; Snieckus, Victor

doi:10.1016/0040-4039(80)80150-x

Cited by 26 publications

(3 citation statements)

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“…The enantioselective access to the more widespread uleine alkaloids with a cis H 15 −H 20 relationship (normal series) required the preparation of a cis -4,5-disubstituted 2-piperidone by stereocontrolled conjugate addition of an appropriate nucleophile to unsaturated lactam 10 , avoiding the undesired equilibration to the more stable trans isomers. Taking into account that metalated dithioacetals have been reported to undergo conjugated addition reactions to unsaturated amides and lactams in fair yields, , we decided to investigate the introduction of the required indolylmethyl substituent on the 4 position of the piperidine ring of lactam 10 by conjugate addition of a 2-(2-indolyl)-1,3-dithiane derivative. It should be mentioned that, although much effort has been devoted to identifying the factors governing the regioselectivity in the addition of sulfur-stabilized anions to enones, there are few reports concerning the stereoselectivity of such conjugate addition reactions 19e.…”

Section: Resultsmentioning

confidence: 99%

Conjugate Additions to Phenylglycinol-Derived Unsaturated δ-Lactams. Enantioselective Synthesis of Uleine Alkaloids

et al. 2004

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The stereochemical outcome of the conjugate addition of a variety of stabilized nucleophiles (2-indoleacetic enolates and sulfur-stabilized anions) to the phenylglycinol-derived unsaturated lactams trans-2, cis-2, and its 8-ethyl-substituted analogue 10 is studied. The factors governing the exo or endo facial stereoselectivity are discussed. This methodology provides short synthetic routes to either cis- or trans-3,4-disubstituted enantiopure piperidines as well as efficient routes for the enantioselective construction of the tetracyclic ring system of uleine alkaloids, both in the normal and 20-epi series. The formal total synthesis of several alkaloids of this group is reported.

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Section: Resultsmentioning

confidence: 99%

Conjugate Additions to Phenylglycinol-Derived Unsaturated δ-Lactams. Enantioselective Synthesis of Uleine Alkaloids

et al. 2004

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“…Hydrogenolysis of 3 gave acid 4 (95% yield), which after an intramolecular Friedel−Crafts reaction, deprotonation, and oxidation gave the anthraquinone derivative of islandicin (5). 5b He extended these findings to design a general route to anthraquinone natural products 7 as well as lignans 8 and indolizidine alkaloids 9 via directed ortho lithiation. The directed metalation of tertiary benzamides proved to have immense synthetic potential and allowed Snieckus and his group to achieve the functionalization of acridones, 10 isocoumarins, 11 and other alkaloids.…”

mentioning

confidence: 99%

“…He extended these findings to design a general route to anthraquinone natural products as well as lignans and indolizidine alkaloids via directed ortho lithiation. The directed metalation of tertiary benzamides proved to have immense synthetic potential and allowed Snieckus and his group to achieve the functionalization of acridones, isocoumarins, and other alkaloids .…”

mentioning

confidence: 99%