An Improved Bekzomorphan Synthesis

A novel Beckmann rearrangement of the 6-mono-oxime of l-methyl-2,3-benzobicyclo[3.2.1]octan-4,6-dione provides the basis for a much improved synthesis of benzomorphans.     

An Improved Synthesis of Brodimoprim

Brodimoprim (1) is a new antibacterial benzylpyrimidine with a broad spectrum of antimicrobial activities. An improved synthetic method of (1) was reported in this paper from 4-bromo-3,5-dimethoxybenzaldehyde (2) through Knoevenagel condensation, 1,3-prototropic isomerization and cyclization with overall yield of 53.8% which was 40.2% in the early report. As a key intermediate, cinnamonitrile (3) was prepared by the condensation of 2 with 3- methoxypropan-enitrile, which was generated in situ from acrylonitrile with methanolic sodium methoxide. It was found that 3 could be converted easily into the corresponding benzyl isomer 4 by reacting with ethylene glycol monomethyl-ether. 4 reacted with guanidine to give 1 without isolation and purification.     

An Improved Synthesis of L-Homohistidine

Bloemhoff - Kerling's method of L-homohistidine synthesis was modified by employing formamidine acetate in liquid ammonia for imidazole ring formation. The improved procedure significantly shortened the synthetic pathway and resulted in enhanced yield.     

An Improved Synthesis of Hexamethylphenalene

The synthesis of 1,3,4,6,7,9-hexamethylphenalene (2) has been improved from 15 steps to a four step procedure. The overall yield has been increased from an estimated 5% to 45%. Key steps in the synthesis are the reaction of 3,5-dimethylbenzylmagnesium chloride with 2,4-pentanedionato lithium in THF to make 5-(3,5-dimethyl-phenyl)-4-methyl-4-hydroxy-2-pentanone (5) and the Lewis acid acylation-alkation of 1,3,6,8-tetramethylnaphthalene using 3-chlorobutanoic chloride in hexane with sonication to make 1,3,4,6,7,9-hexamethyl-phenalane (2).     

三芳基膦配体的合成研究

从间溴苯酚出发, 利用新的合成方法经五步反应合成了一系列具有不同烷氧基的芳基膦配体. 改进后的方法可方便地通用于在苯环上具有各种不同基团基的膦配体衍生物的合成, 且有原料易得、操作简单、产率较高的优点.     

An Improved Synthesis of Ethylidenecyclobutane

In our studies of the chemistry of small rings, it was necessary to synthesize ethylidenecyclobutane 1. Repetition of the only method in the literature^2,3 was attempted, namely, the reaction of 1,1,1-tris-(hydroxymethyl)-propane 2 with phosphorus tribromide to give 1,1,1-tris-(bromomethyl)-propane 3 and the subsequent conversion of 3 to 1 with zinc. The reaction of 2 with phosphorus tribromide is exceedingly hazardous. In spite of the careful adherence to the conditions specified by Derfer, et. al.² there were several fires in the effluent gases and the reaction produced precipitates which ignited spontaneously in air.     

An Improved Synthesis of Dialkylcyclopropenones

Dialkylcyclopropenones are formed in high yields when alkynes are treated with chloroform-butyllithium in THF at - 78 °C followed by acidic hydrolysis of the dichlorocyclopropene intermediates at low temperatures.     

An Improved Synthesis of Tn Antigen

Tn (GalNAc(1?O-Ser/Thr) 6 is a human tumor-associated carbohydrate antigen1. Protein conjugates of Tn antigen have a role for the active specific immunotherapy of cancer. The total synthesis of Tn antigen has been reported2 by glycosidating between 3,4,6-tri-O-acetyl-2-azido-2-deoxy-(-D-galactopyranosyl chloride and L-serine derivative, then removing the protecting groups. In this route, the key intermediate 3,4,6-tri-O-acetyl-2-azido-2-deoxy-(-D-galactopyranosyl chloride was afforded by …     

改进的亚磷酸二乙酯法合成亚甲基二膦酸四乙酯

改进的亚磷酸二乙酯法合成亚甲基二膦酸四乙酯刘国正（北京师范大学化学系北京１００８７５）关键词亚甲基二膦酸四烷基脂，亚磷酸二乙酯，合成ＭＤＰ（ＭｅｔｈｙｌｅｎｅＤｉｐｈｏｓｐｈｏｎａｔｅｓ）的四烷基酯是颇具实用价值的化合物，它与活泼金属反应可生成盐，可...     

An Improved Synthesis of Phospha-Crown Ethers

A synthetic and convenient pathway to phospha-crown ethers is presented involving the condensation of dichlorophenylphosphineoxide with polyethylene glycols under conditions that avoid polymerization.     

An Improved Synthesis of 4-Hydroxypropranolol

An improved synthesis of 4-hydroxypropranolol(4) is described.     

An Improved Synthesis of Dihalopyromellitic Acids

A practical molar scale syntheses of the commercially unavailable dichloro- and dibromopyromellitic acids are described in detail.     

4-氨基吡啶合成方法改进

4-氨基吡啶合成方法改进;甲酰胺基吡啶;降解;水解     

An Improved Synthesis of Conduritol A

Recently Knapp and coworkers¹ reported a highly stereoselective synthesis of the naturally occurring cyclitol conduritol A (1) from p-benzoquinone (2) in 39% overall yield using 9-[(benzyloxy)methoxy]-anthracene (3) as a protecting group (Scheme 1). Although regeneration of the olefinic bond in the product was achieved at room temperature via an oxyanion-accelerated² retro Diels-Alder reaction, this step necessitated protection of the newly introduced groups.     

An Improved Synthesis of 4-Cycloheptenone

A previous paper² described the chemistry of 1-aza-4-cyclo-octene 1 which we prepared from 4-cycloheptenone 2 according to the method of Bahurel et al.³ This procedure involves the condensation of cis-1,4-dichloro-2-butene with ethyl sodio-acetoacetate, yielding, a mixture of four isomers 3–6. The entire mixture is then heated with aqueous potassium hydroxide under reflux for four hours. Under these conditions 5 undergoes decarbethoxylation to yield 4-acetylcyclopentene 7, while 3 yields 2, presumatly by Cope rearrangement atid decarbethoxylation (2 is present in almost negligiblequantity but was reported³ to also yield 2).     

An Improved Synthesis of Trimethylsilylmethyl Isocyanide

Trimethylsilylmethyl isocyanide is prepared by a new method which gives a higher overall yield and circumvents the use of methyl isocyanide.     

二苄叉丙酮合成实验的改进

对二苄叉丙酮的制备实验进行了改进。用氧化铝固载氟化钾代替氢氧化钠作催化剂,研究了醛酮物质的量之比、催化剂用量和溶剂对产率的影响,合成了二苄叉丙酮。该法反应时间短,产率高,操作简便,催化剂可回收再生重复使用。用同样方法合成了其他理,α’-双亚苄基丙酮。     

喹烯酮合成工艺的改进

以邻硝基苯胺为起始原料,经过氧化、Beirut反应、缩合反应3步合成产品喹烯酮,总收率73.4%.产品经HPLC分析,质量分数为98.5%.并通过m.P.、IR、1H NMR和13C NMR确证其结构.     

An Improved Liquid-Phase Synthesis of Simple Alkylpyridines

The synthesis of pyridines from mixtures of aldehydes or ketones NH₃ in the liquid phase has been reinvestigated, using continuous dosage of the carbonyl components to the reaction mixture. The main product from the reaction of acetaldehyde and formaldehyde is 3-methylpyridine ( 6 ), which is also the main product from the reaction of acrolein or a mixture of crotonaldehyde and formaldehyde under the same conditions. The reaction of other aldehydes with formaldehyde give 3,5-dialklypyridines, e.g. 10, 16 . Acetone reacts with either formaldehyde or acetaldehyde to give polysubstituted alkylpyridines. A mechanistic pathway is proposed which accounts for the formation of the observed products.     

An Improved Synthesis of N-Alkoxy-α-Oxo-Arylacetamides

The title compounds can be prepared in good yields in a one-pot procedure from arylglyoxylic acid chlorides, 2-pyridone and O-alkylhydroxylamines.