tertiary C-O bond via asymmetric allylicsubstitution of racemic vinylethylene carbonates with water and alcohols has been developed. Under the cooperative catalysis system of an in situ generated chiral palladium complex and boron reagent in mild conditions, the process allowed rapid access to valuable tertiary alcohols and ethers in high yields with complete regioselectivities and high enantioselectivities
已经开发了一种通过外消旋乙烯基碳酸亚乙酯与水和醇的不对称烯丙基取代对映选择性构建叔 CO 键的有效方法。在温和条件下原位生成的手性钯配合物和硼试剂的协同催化系统下,该过程允许以高产率快速获得有价值的叔醇和醚,具有完整的区域选择性和高对映选择性。该协议代表了与作为氧供体的水直接对映选择性形成三级 CO 键的第一个例子。该过程的合成效用已通过将产品加工成生物相关制剂的关键中间体来证明,
Synthesis of a New (1<i>R</i>)-(−)-Myrtenal-Derived Dioxadithiadodecacycle and Its Use as an Efficient Chiral Auxiliary
作者:M. Elena Vargas-Díaz、Pedro Joseph-Nathan、Joaquín Tamariz、L. Gerardo Zepeda
DOI:10.1021/ol062319f
日期:2007.1.1
[reaction: see text] The new macrocycle 9 (>70% yield from hydroxythiol 10) was treated with several nucleophilic reagents (RMgX, RLi, and LiAlH4) affording carbinols 12a-j (80-96% yield, >99:1 dr). Oxidative hydrolysis of 12a,c,e, followed by LiAlH4 reduction of the resulting mixture, gave 16a,c,e in >95% ee,16c being a key precursor for the preparation of fungicide 17. The absolute configuration
[反应:请参见文本]用几种亲核试剂(RMgX,RLi和LiAlH4)处理了新的大环化合物9(羟基硫醇10的产率> 70%),得到甲醇12a-j(产率80-96%,> 99:1 dr )。12a,c,e的氧化水解,然后将所得混合物进行LiAlH4还原,得到> 95%ee,16c的16a,c,e,这是制备杀菌剂17的关键前体。9和12j的绝对构型( Nu = H)是通过单晶X射线衍射分析和化学相关性建立的。
Asymmetric synthesis of homochiral 1,2-diols via N-boc oxazolidines
Diastereoisomerically pure N-Boc 2-acyloxazolidines were synthesized from phenylglyoxal and ethyl glyoxylate. Reaction of these heterocycles with Grignard reagents is highly stereoselective. Homochiral 1,2-diols were ultimately obtained after N-deprotection, hydrolysis and reduction of the intermediate α-hydroxy aldehyde. The asymmetric induction can be explained by a chelated model.
A New Zincate-Mediated Rearrangement Reaction of 2-(1-Hydroxyalkyl)-1-alkylcyclopropanol
作者:Kenichi Nomura、Seijiro Matsubara
DOI:10.1002/chem.200901054
日期:2010.1.11
A novel rearrangement of 2‐(1‐hydroxyalkyl)‐1‐alkylcyclopropanol has been found. It proceeds in the presence of a catalytic amount of organozinc ate complex to give vic‐diols. The rearrangement can be applied to various types of 2‐(1‐hydroxyalkyl)‐1‐alkylcyclopropanol, which can be easily prepared from the corresponding α,β‐epoxyketones and bis(iodozincio)methane. When bicyclo[13.1.0]pentadecane‐1
phenylglycinol. This preparation involves: (i) a transformation of the above β-amino alcohols into N-Boc 2-ethoxycarbonyloxazolidines, (ii) the formation of the corresponding Weinreb amides and, (iii) a reaction between these amides and organometallic reagents. Such diastereomerically pure heterocycles react cleanly with various nucleophilic reagents (Grinard reagents, sodium borohydride and allylsilane) to afford
N -Boc 2-乙酰基恶唑烷是由去氧麻黄碱和苯基甘醇合成的。该制备涉及:(i)将上述β-氨基醇转化为N。-Boc 2-乙氧基羰基恶唑烷,(ii)形成相应的Weinreb酰胺,和(iii)这些酰胺与有机金属试剂之间的反应。这样的非对映异构纯杂环与各种亲核试剂(格林纳德试剂,硼氢化钠和烯丙基硅烷)干净地反应,得到相应的醇。用三氟乙酸处理这些羟基恶唑烷,然后水解和还原中间体α-羟基醛,得到1,2-二醇。在大多数情况下,整体转化表现出完全的非对映选择性,这可以由用于亲核加成的螯合模型来解释。