Solution 1H and 13C NMR of new chiral 1,4‐oxazepinium heterocycles and their intermediates from the reaction of 2,4‐pentanedione with α‐L‐amino acids and (R)‐(—)‐2‐phenylglycinol

The reaction of 2,4‐pentanedione ( 1 ) with (R)‐(—)‐2‐phenylglycine methyl ester ( 2 ), (R)‐(—)‐2‐phenylglycinol ( 3 ) and the proteinogenic amino acids (2S,3R)‐(—)‐2‐amino‐3‐hydroxybutyric acid (L ‐threonine) ( 4 ) and (R)‐(—)‐2‐amino‐3‐mercaptopropionic acid (L ‐cysteine) ( 5 ) methyl esters was investigated. The corresponding enamines 6 , 7 and 8 were isolated and characterized spectroscopically whereas 9 , which is unstable, was transformed in situ into 13 . Treatment of 7 , 8 and 9 with boron trifluoride etherate afforded the new [1,4]oxazepines 10 , 11 and [1,4]thiazepine ( 12 ) as their BF₃O^? salts. The structures of the enamines and their corresponding seven‐membered heterocycles were assessed by 1D and 2D NMR spectroscopy. Variable‐temperature experiments revealed different molecular mobility behavior among these heterocycles. Copyright © 2003 John Wiley & Sons, Ltd.     

金属离子修饰的铂纳米金属簇催化2,3-戊二酮区域选择性氢化

近年来,α-二酮的不对称氢化引起了人们的极大兴趣[1～3].由于α-二酮分子内存在两个共轭的羰基,α-二酮的氢化包括两步反应,通过控制反应条件可以使反应停留在第一步氢化的阶段[3].在已往的文献报道中[1～3],氢化反应的底物均局限于对称的α-二酮,如2,3-丁二酮或3,4-己二酮.这类底物的第一步氢化并不涉及区域选择性的问题.以2,3-丁二酮为例,第一步氢化只生成3-羟基-2-丁酮一种产物.但是,象2,3-戊二酮之类的不对称α-二酮的氢化情况则复杂得多,因为在第一步反应中有2-羟基-3-戊酮和3-羟基-2-戊酮两种产物生成.因此,在研究不对称α-二酮的对映体选择性氢化时还必须顾及其区域选择性氢化.     

4,6-二甲基-2-取代嘧啶的合成

采用改进的合成方法以乙酰丙酮分别与胍、硫脲、脲反应合成了三种2位杂原子取代的嘧啶类化合物,收率83．8％-98．6％,其结构经1^H NMR,IR和MS表征。     

Copper(Ⅱ)and 1,1 '-Trimethylene-2,2'-biimidazole-promoted Arylation of Acetylacetone with Aryl Iodides

A new and efficient way was developed to carry out the reaction of acetylacetone with aryl iodides under the assistance of Cu(II) and 1,1′‐trimethylene‐2,2′‐biimidazole at 100°C. 3‐Aryl‐2,4‐pentanediones were obtained in excellent yields.     

Synthesis and Crystal Structure of 3,3-Di(acetic ether)-2,4-pentanedione

合成和表征了３，３－二乙酸乙酯基－２，４－戊二酮。得出其为单斜晶系，空间群为Ｃ２／ｃ，ａ＝１４．８６４（２），ｂ＝１０．５６７４（７），ｃ＝９．５０５３（６），β＝１０１．８２５（６）°，υ＝１４６１．１３（２）３，Ｚ＝４，Ｄｘ＝１．２３８ｍｇ／ｍ３，μ＝０．０９８ｍｍ－１，ｆｉｎａｌＲ＝０．０３１４，Ｒｗ２＝０．０８９１     

Sequential Aldol/Michael Addition Reaction in Ionic Liquid Catalyzed by Morpholine: A Convenient Synthesis of 1,3,5‐Triaryl‐1,5‐pentanedione

A series of 1,3,5‐triaryl‐1,5‐pentanediones was obtained via a sequential aldol condensation and Michael addition reaction in ionic liquid catalyzed by morpholine, as a one‐pot reaction. The significance of our findings relates to reducing the use of organic solvents, potentially toxic and hazardous materials, as well as its simplicity, good yields, mild conditions, and lower costs.     

Deconvoluting interspecies bacterial communication

The universal bacterial signal molecule autoinducer-2 (AI-2) is derived from 4,5-dihydroxy-2,3-pentanedione (DPD). DPD exists in a complex equilibrium between multiple forms, and NMR spectroscopy has now been used to establish that the extent of the structural diversity displayed by DPD over a broad pH range is even greater than previously posited.     

5-羟基嘧啶——Ⅴ.1,3-二甲氧基乙酰丙酮与胍和硫脲的缩合

1,3-二甲氧基乙酰丙酮(1)与胍在中性条件下以低产率(28%)缩合生成5-甲氧基-2-氨基-6-甲氧甲基-4-甲基嘧啶(3),而不与硫脲缩合。在与S-甲基异硫脲的反应中,1降解为甲氧基丙酮和甲氧基乙酸,从而生成甲氧基丙酮缩-S-甲基异硫脲甲氧基乙酸盐(4)和S-甲基异硫脲甲氧基乙酸盐(5)。由此可见,1对碱非常敏感,而对酸有一定的稳定性。