Enantio‐ and Diastereoselective,Lewis Base Catalyzed,Cascade Sulfenoacetalization of Alkenyl Aldehydes

A catalytic, enantio‐, and diastereoselective formation of sulfenyl acetals bearing multiple stereogenic centers is reported. Alkenyl aldehydes undergo a chiral thiiranium ion initiated cascade starting with intramolecular capture by a formyl group and termination by capture with HFIP solvent. This method provides a one‐pot synthesis of dihydropyran and 1,3‐disubstituted isochroman acetals in good to excellent yield and with high levels of diastereo‐ (up to >99:1 dr) and enantiocontrol (up to 99:1 er).     

Enantio‐ and Diastereoselective,Lewis Base Catalyzed,Cascade Sulfenoacetalization of Alkenyl Aldehydes

A catalytic, enantio‐, and diastereoselective formation of sulfenyl acetals bearing multiple stereogenic centers is reported. Alkenyl aldehydes undergo a chiral thiiranium ion initiated cascade starting with intramolecular capture by a formyl group and termination by capture with HFIP solvent. This method provides a one‐pot synthesis of dihydropyran and 1,3‐disubstituted isochroman acetals in good to excellent yield and with high levels of diastereo‐ (up to >99:1 dr) and enantiocontrol (up to 99:1 er).     

有机小分子催化的不对称羟醛缩合反应

总结了近年来用于不对称催化羟醛缩合反应的各种有机小分子催化剂, 简要阐述了每种类型的催化剂的催化机理以及它们的优缺点, 同时对有机小分子催化反应的发展进行了展望.     

N-Heterocyclic Carbenes Catalyzed Phospho-Aldol Reaction of Aldehydes

An efficient phospho-aldol reaction of aldehydes catalyzed by N-heterocyclic carbenes （NHCs） has been developed. With 10 mol% stable NHC 1,3-bis（2,6-diisopropylphenyl）imidazol-2-ylidene, various aldehydes reacted with dialkylphosphites smoothly to provide a-hydroxy phosphonates in 59%--99% yield. In this process, NHC was assumed to function as a carbon-centered bronsted base.     

杂双金属复合物ZABDP催化芳香酮与芳香醛的直接不对称Aldol反应

合成了新型的手性铝/锌杂双金属复合物(R,S,S)-3,3'-二[(N-二苯基脯氨醇)甲基]-2,2'-二羟基-1,1'-联萘酚铝/锌复合物(ZABDP).在催化芳香酮与芳香醛的羟醛缩合(Aldol)反应中,该复合物中的铝作为路易斯酸活化醛,锌的烷氧化物作为Br?nsted碱,使苯乙酮形成活性锌的烯醇化物,2种金属的应用使得芳香醛与芳香酮的直接不对称Aldol反应顺利进行,反应的对映选择性最高达90%,产率最高达99%.     

Small Peptides Catalyzed Direct Aldol Reactions of Aldehydes with Hydroxyacetone with Regiocontrol in Aqueous Media

Very recently, we[1] found that L-proline amides and dipeptides acted as efficient catalysts for the asymmetric direct aldol reaction. We report here that L-proline-based peptides 1～5 can catalyze the aldol reactions of hydroxyacetone with aldehydes 6 in aqueous media, to give 1,4-diols (7), the disfavored products with either aldolase or L-proline. Both peptides 3 and 4 give good results.     

脯氨酸二肽催化的不对称直接Aldol反应

以(S)-脯氨酸和(R)-脯氨酸为原料合成了二肽H-(S)-Pro-(S)-Pro-OH(1)和H-(S)-Pro(-R)-Pro-OH(2),分别以两种二肽催化了不对称直接A ldol反应,获得了相同立体构型(S)的产物,与(S)-脯氨酸催化所得的产物构型(R)相反.该催化剂的立体选择性不高(ee<21%).理论计算的结果与实验结果吻合.     

联二萘酚衍生手性二胺催化的不对称Aldol反应

在10 mol%手性二胺和10 mol%手性磷酸的催化下,苯乙酮及其衍生物与三氟丙酮酸甲酯完成Aldol反应,得到80%的产率和73%ee的对映体过量产物,其结构经1H NMR和13C NMR表征.     

L-脯氨酸催化的不对称Aldol缩合反应实验设计

介绍了L-脯氨酸催化的对硝基苯甲醛与丙酮的不对称Aldol反应的实验设计。室温反应2 h后,柱层析得到（R）-4-（4-硝基苯基）-4-羟基-2-丁酮,利用手性高效液相色谱测试得到产物的ee值。学生实验结果显示,收率范围为53%~74%,对映选择性范围为62%~69%。本实验方案将Aldol反应的研究成果设计成综合性实验,不仅强化训练了学生基本的实验技能和操作,同时拓宽了知识面,培养了学生分析问题、解决问题等方面的综合能力。     

Enantioselective Aldol Reaction with Difluoroenoxysilanes Catalyzed by Cationic Palladium Aqua Complexes

The enantioselective addition of difluoroenoxysilanes to aromatic aldehydes, catalyzed by cationic palladium aqua complexes, has been described. The reaction is operationally simple, does not require anhydrous conditions and performs at room temperature. The palladium catalysts, previously discovered and reported by Sodeoka, are easily prepared in two steps from PdCl₂(MeCN)₂. The aldol compounds were obtained in good yields and with enantiomeric ratios up to 93 : 7, the reaction being more efficient using electron-rich aldehydes.     

Proline‐Tetrazole‐Catalyzed Enantioselective N‐Nitroso Aldol Reaction of Aldehydes with In Situ Generated Nitrosocarbonyl Compounds

A highly enantioselective method (up to 98 % ee) for the preparation of β‐amino alcohols was achieved by using the readily available proline‐tetrazole as the catalyst for the N‐nitroso aldol reaction of aldehydes with in situ generated nitrosocarbonyl compounds. The key to success of this reaction is the use of MnO₂ as an oxidant and catechol as a Brønsted acid additive.     

CuCl／Zn-promoted Mukaiyama Aldol Reaction of Phenyl a-fluoro silyl enol ether with Aldehydes

2-Fluoro-l-phenyl-l-trimethylsiloxyethene reacted efficiently with aldehydes to give a-fluoro β-hydroxy ke-tones in HMPA in the presence of Zn powder and CuCl.