Pt-catalyzed tandem epoxide fragmentation/pentannulation of propargylic esters

Journal of the American Chemical Society

Volumn 128, Issue 21, 2006, Pages 6786-6787

  Pujanauski, Brian G ^a   Bhanu Prasad, B A ^a   Sarpong, Richmond ^a  

^a UNIVERSITY OF CALIFORNIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

4 CHLOROBENZOIC ACID; AMPHOLYTE; EPOXIDE; ESTER; HYDROGEN; PLATINUM; PROPARGYLIC ESTER; PYRAN DERIVATIVE; UNCLASSIFIED DRUG;

ANNULATION REACTION; ARTICLE; CATALYSIS; CATALYST; CHEMICAL BOND; CHEMICAL STRUCTURE; CYCLIZATION; DIASTEREOISOMER; HEATING; PENTANNULATION REACTION; REACTION ANALYSIS; STEREOCHEMISTRY; STRUCTURE ANALYSIS; SYNTHESIS;

CATALYSIS; CHEMISTRY, ORGANIC; EPOXY COMPOUNDS; ESTERS; PLATINUM; PYRANS; STEREOISOMERISM;

EID: 33744801116     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja061549m     Document Type: Article

References (28)

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15. To the best of our knowledge, transformations of the type 8-9 are unprecedented.
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19. For experimental details of the synthesis of substrates 10, 13, and 16, see Supporting Information.
20. Obtained as an inseparable mixture (1:1.2) of 11a and 11b, respectively.
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22. 2 alone effects the conversion 13→15 over prolonged heating (=12 h).
23. The conversion 13→14 likely proceeds via 24, which results from an initially formed allenyl intermediate 23. For Pt(II)-catalyzed reactions of propargylic esters bearing a phenyl at the alkyne terminus, see: Cariou, K.; Mainetti, E.; Fensterbank, L.; Malacria, M. Tetrahedron 2004, 60, 9745-9755.
24. Substrates similar to 13 bearing either a cyclopropane or 1-cyclohexene at the terminus of the alkyne demonstrated analogous reactivity.
25. The secondary propargylic acetate 25 bearing a terminal alkyne is also efficiently converted to cyclopentenone 26 under Pt(II) catalysis.
26. The ORTEP depiction of 19 is enantiomeric to the structure drawn in Scheme 2. Stereoviews and crystallographic data are in the Supporting Information.
27. 2, pyran 20 remained unchanged upon heating.
28. 2) and monitoring aliquots of the reaction mixture at 3-h intervals, initially observed proton resonances characteristic of dienone and pyran intermediates converged over 10 h at 100 °C to resonances corresponding to bicycles 11a and 11b.