Stepwise acid-promoted double-Michael process: An alternative to Diels-Alder cycloadditions for hindered silyloxydiene-dienophile pairs

Organic Letters

Volumn 9, Issue 2, 2007, Pages 375-378

  Jung, Michael E ^a   Ho, David G ^a  

^a UNIVERSITY OF CALIFORNIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ALKADIENE; ALUMINUM DERIVATIVE; CYCLOHEXANONE DERIVATIVE; IMIDE; TRIFLIMIDE; TRITERPENE; UNCLASSIFIED DRUG;

ARTICLE; CATALYSIS; CHEMICAL STRUCTURE; CHEMISTRY; CYCLIZATION; HYDROLYSIS; STEREOISOMERISM; SYNTHESIS;

ALKADIENES; ALUMINUM COMPOUNDS; CATALYSIS; CYCLIZATION; CYCLOHEXANONES; HYDROLYSIS; IMIDES; MOLECULAR STRUCTURE; STEREOISOMERISM; TRITERPENES;

EID: 33846610058     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol062980j     Document Type: Article

References (24)

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8. It is somewhat difficult to find references to the problems caused by severe steric hindrance in intermolecular Diels-Alder reactions, but one can find examples where the conditions for the successful cycloaddition are quite harsh. See for example: (a) Engler, T. A.; Sampath, U.; Vander Velde, D.; Takusagawa, F. Tetrahedron 1992, 48, 9399-16.
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14. a) Jung, M. E.; Davidov, P. Angew. Chem. 2002, 41, 4125-28.
15. a of triflimide is estimated to be -16 while that of triflic acid has been calculated to be -14. Bordwell, F. G. Acc. Chem. Res. 1988, 21, 456-463.
16. (a) Narasaka, N.; Soai, K.; Aikawa, Y.; Mukaiyama, T. Bull. Chem. Soc. Jpn. 1976, 49, 779-83.
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18. For an example of a triflimide-promoted Michael addition (and closure to the [2+2] product), see: Takasu, K.; Ishii, T.; Inanaga, K.; Ihara, M. Org. Synth. 2006, 83, 193.
19. Mathieu, B.; Ghosez, L. Tetrahedron Lett. 1997, 38, 5497-5500.
20. The enone ester is prepared from 3-ethoxycyclohexenone by alkylation of the anion (LDA) with ethyl bromoacetate, followed by addition of methyl Grignard reagent and hydrolysis in an overall yield of 79%. See: Horiguchi, Y.; Nakamura, E.; Kuwajima, I. J. Am. Chem. Soc. 1989, 111, 6257-65.
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24. This diene is prepared from 2-acetyl-1,3,3-trimethylcyclohexene in good yield. See: Jung, M. E.; Murakami, M. Org. Lett. 2006, 8, 5857-59.