Lewis base activation of Grignard reagents with N-heterocyclic carbenes. Cu-free catalytic enantioselective additions to γ-chloro-α,β- unsaturated esters

Journal of the American Chemical Society

Volumn 128, Issue 49, 2006, Pages 15604-15605

  Lee, Yunmi ^a   Hoveyda, Amir H ^a  

^a BOSTON COLLEGE   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

CARBENOID; CHLORINE DERIVATIVE; COPPER; ESTER DERIVATIVE; GRIGNARD REAGENT; HETEROCYCLIC COMPOUND; LEWIS BASE; REAGENT;

ADDITION REACTION; ALKYLATION; ARTICLE; CATALYSIS; CHIRALITY; COMPLEX FORMATION; CRYSTAL STRUCTURE; DIASTEREOISOMER; ENANTIOSELECTIVITY; REACTION ANALYSIS;

ALLYL COMPOUNDS; CATALYSIS; COPPER; ESTERS; HETEROCYCLIC COMPOUNDS; HYDROCARBONS; HYDROCARBONS, CHLORINATED; MAGNETIC RESONANCE SPECTROSCOPY; METHANE; MOLECULAR STRUCTURE; STEREOISOMERISM;

EID: 33845432746     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja067456m     Document Type: Article

References (25)

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21. Byproducts 4 and 9 are formed in <2% ee (see the Supporting Information for details).
22. 2O) are more efficient (0.5 mol %, >98% in 1 h) but less selective. For example, reaction of 1b with i-PrMgCl delivers 2b with 5.5:1 regioselectivity (vs 9:1 with 7) and in 89% ee (vs 97% with 7). Details will be reported in a separate account.
23. 2Mg affords 2a in 94% ee and 4:1 regioselectivity (95% conversion, 24% 4; Table 1 conditions).
24. For example, reaction of allylic chloride 1a with 1.0 equiv 7 and 2.0 equiv i-PrMgCl leads to <2% conversion.
25. Similar arguments can account for high activity of NHC·Cu complexes (e.g., ref 6). It is direct complexation/activation of a nontransition, and especially an early, metal by an NHC that has not been previously utilized.