比较开链仲,仲-1,2-二醇的双-(R)-或双-(S)-MPA酯衍生物的室温和低温1 H NMR光谱,可轻松确定其相对立体化学,有时甚至是绝对构型。如果二醇是抗性的,则其绝对构型可以直接从ΔδT1T2的符号推导出对于取代基R 1 / R 2,但如果二醇的相对立体化学是顺式,则其绝对构型的分配需要制备两种衍生物(双-(R)-和双-(S)-MPA酯) ,其室温的比较1 1 H NMR谱,并计算该Δδ的RS次甲基Hα(R 1)和Hα(R 2)和R 1 / R 2质子的符号。这些相关性的可靠性通过用作模型化合物的已知绝对构型的17种二醇进行了验证。
A Useful Synthetic Equivalent of a Hydroxyacetone Enolate
摘要:
Indium promoted allyiation of carbonyl compounds with 4-(bromomethyl)-1,3-dioxol-2-one diastereoselectively affords and-alpha,beta-dihydroxyketones, protected as enol carbonates. These initial products can be deprotected to free dihydroxyketones or transformed under mild conditions Into the corresponding cyclic carbonates, which constitutes a useful approach to hydroxyacetone aldois.
The aldolreaction of hydroxyacetone with different aldehydes usingimmobilizedproline on a mesoporoussupport, assisted by heat and microwaves, has been explored. It was found that heterogenized L-proline on MCM-41 catalyzed aldolreactions in both hydrophilic and hydrophobic solvents, and provided stereoselectivities in some cases complementary to the homogeneous catalyst. The heterogeneous catalysts
Amino Acid Catalyzed Direct Asymmetric Aldol Reactions: A Bioorganic Approach to Catalytic Asymmetric Carbon−Carbon Bond-Forming Reactions
作者:Kandasamy Sakthivel、Wolfgang Notz、Tommy Bui、Carlos F. Barbas
DOI:10.1021/ja010037z
日期:2001.6.1
lack of nonlinear effects. The reactions tolerate a small amount of water (<4 vol %), do not require inert reaction conditions and preformed enolate equivalents, and can be conveniently performed at room temperature in various solvents. In addition, reaction conditions that facilitate catalyst recovery as well as immobilization are described. Finally, mechanistically related addition reactions such as
Additive-controlled regioselective direct asymmetric aldol reaction of hydroxyacetone and aldehyde
作者:Ling-yan Liu、Bing Wang、Yunna Zhu、Wei-xing Chang、Jing Li
DOI:10.1016/j.tetasy.2013.03.018
日期:2013.5
developed for the directasymmetricaldolreaction of hydroxyacetone and various aldehydes with moderate to high yields and high enantioselectivities. More importantly, this regioselective reaction could be easily regulated by changing the additives in the presence of the same organocatalyst 1b, to afford the normal 1,2-diol adducts and the disfavoured 1,4-diol products, respectively, in a highly regioselective
Insights into Substituent Effects of Benzaldehyde Derivatives in a Heterogeneous Organocatalyzed Aldol Reaction
作者:Graziano Di Carmine、Fabio Pesciaioli、Simeng Wang、Arianna Sinibaldi、Giuliana Giorgianni、Christopher M. A. Parlett、Armando Carlone、Carmine D'Agostino
DOI:10.1002/cctc.202200405
日期:2022.7.21
heterogenous organocatalysis is undoubtedly critical to develop new and higher performing catalysts. NMR relaxation techniques provide very useful insights into adsorption effects of the aldehyde partner in an organocatalyzed aldol reaction.
An efficient organo-catalytic, highly syn-stereoselective method for aldol additions between enolizable aldehydes and hydroxyacetone as well as dihydroxyacetone is disclosed. Reactions proceed in the presence of tertiary amines at room temperature. The aldol adducts can be obtained in good to high yields and with high degrees of syn-diastereoselectivity. This new aldol reaction provides an operationally simple protocol for the stereocontrolled synthesis of carbohydrates