Catalytic enantioselective tautomerization of isolated enols

Angewandte Chemie - International Edition

Volumn 46, Issue 37, 2007, Pages 7119-7121

  Fehr, Charles ^a  

^a Analysis and Perception Department   (Switzerland)

Author keywords

Enantioselective protonation; Enols; Grignard reagents; Ketenes; Odoriferous compounds

Indexed keywords

CATALYST ACTIVITY; ENANTIOSELECTIVITY; KETONES; PROTONATION; SYNTHESIS (CHEMICAL);

CATALYTIC ENANTIOSELECTIVE TAUTOMERIZATION; ENANTIOSELECTIVE PROTONATION; GRIGNARD REAGENTS; ISOLATED ENOLS; ODORIFEROUS COMPOUNDS;

ALCOHOLS;

EID: 34848899856     PISSN: 14337851     EISSN: None     Source Type: Journal    
DOI: 10.1002/anie.200701428     Document Type: Article

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35. 2O ("Karl Fischer" method). It was not possible to rigorously dry 7 in toluene/THF in the presence of 4A molecular sieves as these conditions resulted in rapid ketonization. For determination of the enol content, air was bubbled through a sample of enol solution (room temperature for 5 min), thus affording γ-oxygenated products (primarily the hydroperoxide). These represent 97-98% by GC and ketone 4 amounts to 2-3%. Nonvolatile by-products: approximately 5%.
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38. 2O to 1 in THF at -70°C affords a 3:1 mixture of (E/Z)-8(Li) which is unsuitable for enantioselective protonation (74% ee!).
39. Under these conditions, accumulation of transient 9 is avoided; see reference [3e].
40. The absolute configuration of (S)-10 was determined by independent synthesis (PhLi + p-chlorothiophenylester of (S)- α-cyclogeranic acid (Ref. [3g]).