A series of novel bifunctional phosphine sulfonamide organic catalysts were designed and readily prepared from natural amino acids, and they were utilized to promote enantioselective aza-Morita-Baylis-Hillman (MBH) reactions. L-Threonine-derived phosphine-sulfonamide 9b was found to be the most efficient catalyst, affording the desired aza-MBH adducts in high yields and with excellent enantioselectivities.
Catalytic Synthesis of γ-Lactams via Direct Annulations of Enals and N-Sulfonylimines
摘要:
Cinnamaldehydes and N-sulfonylimines undergo direct annulations to cis-disubstituted gamma-lactams via the intermediacy of catalytically generated homoenolates. Critical to the success of this process was overcoming inhibition of the N-heterocyclic carbene catalyst by the electrophilic imines. The overall process proceeds with good yields and diastereoselectivites and requires no stoichiometric reagents or additives.
a critical step affecting the efficiency of the NHC‐catalyzed γ‐butyrolactone formation via homoenolate addition to aryl aldehydes. A novel type of imidazolylidene catalyst with pendant alkoxy groups on the ortho‐N‐aryl groups is described. Catalyst of this sort facilitates the formation of the conjugated Breslow intermediate. Studies of the rate constants for homoenolate annulation affording γ‐butyrolactones
Synthesis of an <i>N</i>-Mesityl Substituted Chiral Imidazolium Salt for NHC-Catalyzed Reactions
作者:Justin R. Struble、Juthanat Kaeobamrung、Jeffrey W. Bode
DOI:10.1021/ol800006m
日期:2008.3.1
A new synthetic approach to chiralimidazoliumsalts makes possible the first synthesis of an N-mesityl substituted, aminoindanol-derived N-heterocycliccarbeneprecursor, 1.ClO4. The successful synthesis allows the first direct comparison of otherwise identical imidazolium and triazolium precursors across a number of NHC-catalyzed processes. These studies confirm striking differences in reactivity