The stereoselective construction of quaternary stereogenic centers is described that employs an allylic substitution through the intermediacy of a chiral carbamate leaving group. Five carbamates with two substituents at the allylic terminus combined with phenylcopper or n-butylcopper to provide alkenes in moderate to good yields and with moderate to high enantioselectivities at the newly created quaternary stereogenic center. The E-carbamate with methyl and cyclohexyl substituents at the gamma-terminus provided the highest yield (87%) and enantioselectivity (>99.9:0.1 er) of all the substitution patterns tested. The corresponding Z-carbamate gave the lowest enantioselectivity observed (80.0:20.0). Carbamates with other substituents (n-butyl and t-butyl) at the E-terminal position gave moderate yields and enantioselectivities of alkenes. Cinnamyl substrates also provided good yields of alkenes with moderate enantioselectivities. The origin of enantioselectivity is analyzed in the context of dimeric lithioheterocuprate structures.
Rhenium-Catalyzed 1,3-Isomerization of Allylic Alcohols: Scope and Chirality Transfer
作者:Christie Morrill、Gregory L. Beutner、Robert H. Grubbs
DOI:10.1021/jo061436l
日期:2006.9.1
The scope of the triphenylsilyl perrhennate (O3ReOSiPh3, 1) catalyzed 1,3-isomerization of allylicalcohols has been thoroughly explored. It was found to be effective for a wide variety of secondary and tertiary allylicalcohol substrates bearing aryl, alkyl, and cyano substituents. Two general reaction types were found which gave high levels of product selectivity: those driven by formation of an
Highly Selective 1,3-Isomerization of Allylic Alcohols via Rhenium Oxo Catalysis
作者:Christie Morrill、Robert H. Grubbs
DOI:10.1021/ja044054a
日期:2005.3.9
strategies are developed to promote the highlyselective 1,3-isomerization of a variety of allylic alcohols using O3ReOSiPh3 as a catalyst. The first strategy utilizes substrates whose 1,3-regioisomer contains a conjugated alkene, which relies on thermodynamics to obtain high selectivity. The second strategy employs N,O-bis(trimethylsilyl)acetamide as an additive to selectively and irreversibly remove the product
Hydride reduction of alpha, beta-unsaturated carbonyl compounds using chiral organic catalysts
申请人:MacMillan David
公开号:US20060161024A1
公开(公告)日:2006-07-20
Nonmetallic, chiral organic catalysts are used to catalyze the 1,4-hydride reduction of an α,β-unsaturated carbonyl compound. The α,β-unsaturated carbonyl compound may be an aldehyde or cyclic ketone, and the hydride donor may be a dihydropyridine. The reaction is enantioselective, and proceeds with a variety of hydride donors, catalysts, and substrates. The invention also provides compositions effective in carrying out the 1,4-hydride addition of α,β-unsaturated carbonyl compounds.
Full details of a stereodivergent hydroboration of allenes are reported. While hydroboration of an allene with 9‐BBN provided a thermodynamically stable (E)‐allylic alcohol after oxidative work‐up, the reaction of an identical allene with HB(Sia)2 (disiamylborane) formed a (Z)‐allylic alcohol as the kinetic product. The developed conditions allowed for the synthesis of trisubstituted olefins in a highly
Asymmetric Hydrogenation of Allylic Alcohols Using Ir–N,P-Complexes
作者:Jia-Qi Li、Jianguo Liu、Suppachai Krajangsri、Napasawan Chumnanvej、Thishana Singh、Pher G. Andersson
DOI:10.1021/acscatal.6b02456
日期:2016.12.2
γ-disubstituted and β,γ-disubstituted allylicalcohols were prepared and successfully hydrogenated using suitable N,P-based Ir complexes. High yields and excellent enantioselectivities were obtained for most of the substrates studied. This investigation also revealed the effect of the acidity of the N,P–Ir-complexes on the acid-sensitive allylicalcohols. DFT ΔpKa calculations were used to explain the effect of