One-Step Cyclization: Synthesis of N-Heteroalkyl-N'-tosylpiperazines

Piperazine derivatives are important intermediates in organic synthesis and useful building blocks in pharmaceutical and fine chemical industries. Currently available synthetic routes for these heterocyclic compounds have limited scope owing to the harsh reaction conditions, low yields, and multistep process. Herein, we reported a practical method for synthesis of alkyl-, alcohol-, amine-, and ester-extended tosylpiperazines under mild conditions with moderate to high yields. This protocol exhibits potential applicability in the synthesis of pharmaceuticals and natural products because of the operational simplicity and the conveniently available reactants. On the basis of the experimental and theoretical results, a plausible mechanism of aliphatic nucleophilic substitution (S(N)) in the cyclization has been postulated and evidence for the formation of a six-membered ring has also been confirmed by means of density functional theory (DFT) calculations.     

A Cyclic Sulfate Approach to the Synthesis of 1,4-Dideoxy-1,4-imino Derivatives of L-Xylitol,L-Arabinitol and D-Xylitol

Polyhydroxylated pyrrolidines are readily accessible by ring opening of a 1,4-cyclic sulfate function in pentitol derivatives by nitrogen nucleophiles and further processing of the in situ generated charged sulfate group.     

New Cyclization Route to the Skeletons of Lennoxamine and Chilenine

A new cyclization route, triggered by epoxide opening, has been performed to provide the key intermediates for isoindolobenzapine alkaloids, lennoxamine and chilenine. The epoxide was prepared by the Stille reaction using vinyltributylstannane and the following dioxirane treatment. Cyclization under the treatment of BF₃ · OEt₂ provided an azepine moiety, and the oxidative cyclization toward the known precursor for the alkaloids has been achieved by reaction with a stoichiometric amount of Pd(OAc)₂. This formal synthesis suggests a new route to the alkaloids.     

A New Route to 1,3-Dienes: TMSI Elimination of 2-Ene-1,4-diols

Iodotrimethylsilane effects conversion of acyclic bis-secondary 2-ene-1,4-diols to 1,3-dienes in moderate yield. The reaction with 3-hexene-2,5-diol favors anti elimination but is largely nonstereospecific.     

Biomimetic Cyclization of Enamide-Containing Polyenes as a New Route to Azapolycycles

Enamide 4 was studied for its effectiveness as a polyene precursor in biomimetic cyclizations. While most conventional Lewis acids were poor cyclization promoters, FeCl(3).6H(2)O initiated the conversion of 4 into tricycles 6 and 7 in excellent yield. The two isomeric products result from the cyclization of intermediate aldehyde 5 by either a chair or boat B-ring transition state. These results suggest that enamides may be incorporated into polyene precursors for the construction of larger azapolycycles such as azasteroids.     

Ugi/原子转移自由基环合反应合成γ-丁内酰胺的研究

将碘乙酸、烯丙基胺、芳香醛和异腈室温下在甲醇中进行多组分Ugi反应得到加合物,进一步在二氯甲烷中以三乙基硼为引发剂,进行α-酰胺基自由基原子转移5-exo环合反应,可以得到γ-丁内酰胺,操作简便,产率中等.     

A New Route for the Synthesis of 1,4-Dicarbonyl Compounds: Synthesis of Jasmone,Dlhydrojasmone and a Prostaglandin Intermediate

1,4-Dicarbonyl compounds are versatile intermediates for the synthesis of a variety of natural products such as jasmonoids, prostanoids, steroids and terpenoids having a cyclopentenone or furan ring system. Although many synthetic routes for the preparation of these compounds are known and continue to appear¹, most of the existing methods involve lengthy procedures and are limited to the synthesis of 1,4-diketones. Herein, we report a convenient three step approach for the synthesis of 1,4-dicarbonyl compounds starting from tosyl methyl isocyanide² (TosMIC). This method is general for the preparation of 1,4-ketoaldehydes as well as 1,4-diketones.     

A Route to Optically Active Trisubstituted Pyrrolidines using Claisen Rearrangements of Azalactones.

Chiral trisubstituted pyrrolidines [(13a) and (13b)] are obtained exclusively by Ireland enolate Claisen rearrangement of the corresponding azalactones [(12a) and (12b)].     

烯烃羰化—步制醇铑系催化新体系的研究

羰基铑催化剂由于其加氢性能较弱，在羰基化反应的研究中，通常仅作为烯烃氢甲酰化制醛的催化剂。产物中得不到醇。本文则报道了以Ｒｈ＿２（ＡｃＯ）＿４和Ｒｈ＿６（ＣＯ）＿１６为催化剂，在一个反应器内进行烯烃氢甲酰化，加氢制醇的研究。系统考察了Ｒｈ／Ｐｂｕ＿３／ＥｔＯＨ催化体系受各种反应条件的影响。在最佳反应条件下，烯烃转化率达１００％。对醇选择性亦在９９．５％以上，正异构比在２以上．为烯烃一步制醇建立了铑系催化新体系。文中并利用红外光谱测定了反应过程的催化剂物种．实验证明，由烯烃一步制醇是由烯烃首先进行氢甲酰化反应，然后由生成的醛进一步加氢成醇的一个串联反应过程。前一步骤反应速度较快，２ｈ内可使９５％以上的烯烃转化为醛，后面由醛加氢成醇则进行缓慢，在１００—１２０℃下，至少２２ｈ，才能使醛全部转化为醇。     

Ni-Catalyzed Cyclization of Enynes and Alkynylboronates: Atom-Economical Synthesis of Boryl-1,4-dienes

We report a novel atom-economical Ni-catalyzed cyclization reaction of enynes with alkynylboronates. The reaction employs a non-expensive Ni salt, a phosphine-based ligand and easy-handling alkynylboronates as boron–carbon source. The reaction provides complex fused-bicyclic compounds containing borylated 1,4-cyclohexadienes in high yields in short reaction times, involving the formation of two C−C bonds in one step. A reasonable reaction mechanism is proposed based on mechanistic experimental results.     

邻芳基苯基膦酸酯的新合成路线

以磷酸苯酯为原料,经碱性重排、O-磺酰化和Suzuki偶联反应合成邻芳基苯基膦酸酯是一条方便合理的路线.     

A New Route for Synthesis of Entecavir

2-Amino-1,9-dihydro-9-[(1S,3R,4S)-4-hydroxy-3-(hydroxymethyl)-2-methylenecyclopen tyl]-6H-purin-6-one (entecavir, Scheme 1) is a novel carbocyclic 2-deoxyguanosine analog drug which has potent and selective anti hepatitis B virus (HBV) activity1-3. Entecavir is also effective against lamivudine-resistant YMDD mutants4. The US Food and Drug Administration (FDA) approved entecavir as a new preferred drug for the treatment of HBV after lamivudine in March, 2005. Scheme 1 The structure o…     

A Facile Route to Rapid Synthesis of Soluble Monodisperse Oligo(1,4-phenyleneethynylene)s

Introduction Recently, much attention has been paid to monodisperse, well-defined conjugated oligomers as candidates for molecular wires and molecular scale electronic devices[1-7]. Shape persistent oligo(1,4-phenyleneethynylene)s are especially attractive for their excellent main-chain rigidity and interesting electronic characteristics[3-7]. Different iterative divergent/convergent routes have been reported by several groups for the rapid synthesis of oligo(1,4-phenyleneethynylene)s. Godt et al.[5]     

Cyclization of Chlorosulfonyl Isocyanate with Phenylhydrazones: A Synthetic Route to Triazinonoxathiazinedioxides and Triazinones

A convenient synthetic route is reported for the preparation of aroyl substituted triazinones and triazinono-xathiazinedioxides by the interaction of chlorosulfonyl isocyanate and phenylhydrazones (derived from acetylacetone, 1-benzoylacetone and dibenzoylmethane).     

A Facile Route to Rapid Synthesis of Soluble Monodisperse Oligo （1,4-phenyleneethynylene） s

Recently, much attention has been paid to monodisperse, well-defined conjugated oligomers as candidates for molecular wires and molecular scale electronic devices. Shape persistent oligo ( 1,4-phenylene-ethynylene) s are especially attractive for their excellent main-chain rigidity and interesting electronic characteristics.     

Cobalt-Catalyzed Cyclization of 2-Bromobenzamides with Carbodiimides: A New Route for the Synthesis of 3-(Imino)isoindolin-1-ones

A novel synthetic pathway to approach 3-(imino)isoindolin-1-ones by the Co-catalyzed cyclization reaction of 2-bromobenzamides with carbodiimides has been developed. This catalytic reaction can tolerate a variety of substituents and provide corresponding products in moderate yields for most cases. According to the literature, the reaction mechanism is proposed through the formation of a five-membered aza-cobalacycle complex, which carries out the following reaction subsequence, including nucleophilic addition and substitution, to furnish the desired structures.     

The Photoaddition of Aldehydes to Enones: A Direct Route to 1,4-Diketones

Recent work in this² and other³ laboratories has shown that the photochemically-induced addition of oxy-carbinyl species to enones provides a simple and effective method of carbon-carbon bond formation. Thus addition of alcohols^2C,3,4 and acetals^2a to enones (e. g. 1 or 4) affords keto-alcohols (e. g. 2 or 5) and keto-ketals (e. g. 6), the synthetic value of which are enhanced by the fact that the functionalities are conveniently differentiated, thereby facilitating selective manipulation.⁵     

A New Route to the Synthesis of Alpha-Alkyltetrahydrothiophene-1,1-Dioxide Compounds

Alpha-alkyltetrahydrothiophene-1,1-dioxide compounds have been prepared in relatively high yield through the reaction of 2-lithiotetrahydrothiophene-1,1-dioxide with primary alkyl halides.