A new synthesis of pyrrole derivatives from tris(isopropylthio)cyclopropenylium perchlorate and thioureas

The reaction of tris(isopropylthio)cyclopropenylium perchlorate ( 1 ) with sodium thioureides 3a-c , prepared from thioureas 2a-c and sodium hydride, in dry acetonitrile gave the pyrrole derivatives 4a-c , respectively, in high yields.     

A new synthetic route to α-alkylacrylic esters and α-alkylacrylonitriles

α-Alkylacrylic esters and α-alkylacrylonitriles have been synthesized by cracking their cyclopentadiene adducts. The latter were derived by treatment of the lithium enolates of cyclopentadiene-blocked acrylates or acrylonitriles with alkyl halides.     

The reaction of enamines with β-ketoesters: A route to γ-pyrones

β-Ketoesters and enamines are found to react at elevated temperatures to give γ-pyrones in yields of 10 to 50%.     

Reaction of α,β-unsaturated carbodiimides with enamines leading to fused pyridine derivatives

The treatment of (5,5-dimethyl-3-oxo-1-cyclohexenyl)iminotriphenylphosphorane ( 2 ) with phenyl isocyanate ( 3a ) gave N-(5,5-dimethyl-3-oxo-1-cyclohexenyl)-N'-phenylcarbodiimide ( 4a ) in situ. The reaction of 4a with enamines proceeded smoothly to afford the pyridine ring formation with the elimination of amine. This means that 4a is regarded as a new class of 2-aza-1,3-butadiene. The scopes and limitation of this reaction are also discussed.     

A convenient route to α-amido-β-lactams

Dedicated to Professor John C. Sheehan on the occasion of his sixty-fifth birthday. A method for the synthesis of α-amido-β-lactams without the intermediacy of an α-amino-β-lactam is described. The appropriate β-keto ester is used for preparing a vinylamino β-lactam via a “Dane salt” by a previously reported method. Oxidation with ruthenium tetroxide and periodic acid of this product leads directly to the desired “V”, or “G” or analogous α-amido side chain.     

Access to aza-γ-carbolines by annulation reaction of amino derivatives of imidazo[1,2-α]pyridine

Different routes of formation of aza-γ-carboline ring-system are discussed. In addition the reactivity of an amino derivative in comparison with an iminophosphorane compound is investigated.     

α-Hydroxyacylation of pyridine

Efficient synthesis of 2-α-hydroxyacylpyridines 10 starting from pyridine N-oxide and 2-bromoaldehydes via base-induced rearrangement of the resulting N-alkoxypyridinium salts 6 is described.     

Coupling reaction of poly(α-methylstyryl) anion with (MMA–α-methylstyrene) block copolymer

(MMA–α-methylstyrene)block copolymer was reacted with poly(α-methylstyryl)anion at ?78°C in a mixture of good tetrahydrofuran (THF) and poor methylcyclohexane solvents. The reaction conditions were chosen so as to produce graft copolymers made up of a backbone (AB-type block copolymer) and a single branched chain (1:2 graft copolymer). Gel permeation chromatograph (GPC), osmotic pressure measurement, and elemental analysis were used for the characterization of 1:2 graft copolymer. It appeared that poly(α-methylstyryl)anion reacted with the end pendant groups located farthest away from the branched point of AB-type block copolymer, when the dimensions of AB-type block copolymer molecule are small.     

Short synthesis of tryptophane and β-carboline derivatives by reaction of indoles with N-(diphenylmethylene)-α,β-didehydroamino acid esters

The ethylaluminum dichloride catalyzed Michael-type addition of indoles 1a-h to the N-(diphenylmethylene)-α,β-didehydroamino acid esters 2a-c allows a new synthesis of β-methyltryptophanes 41,m and a new route for 1,1-diphenyl-3-carbalkoxy-1,2,3,4-tetrahydro-β-carbolines 5a-m.     

Amine-induced rearrangements of 2-bromo-1-(1H-indol-3-yl)-2-methyl-1-propanones: A new route to α-substituted indole-3-acetamides, β-substituted tryptamines, α-substituted indole-3-acetic acids and indole β-aminoketones

The reaction of 2-bromo-1-(1H-indol-3-yl)-2-methyl-1-propanone ( 1 ) and 2-bromo-1-(1-methyl-1H-indol-3-yl)-2-methyl-1-propanone ( 2 ) with primary amines proceeds in good yields to produce rearranged amides by a proposed pseudo-Favorskii mechanism. These amides in turn can either be reduced to produce β-substituted tryptamines or hydrolyzed to produce substituted indole-3-acetic acids. When the reaction is carried out using bulky primary or secondary amines, β-aminoketones are produced by elimination of hydrogen bromide followed by Michael addition. When hindered secondary amines or tertiary amines are used, elimination to the α,β-unsaturated ketones occurs.     

Nucleophilic addition of organocerium reagents to α‐alkoxy hydrazones: A new type of elimination reaction to α‐hydroxynitriles

We studied the nucleophilic addition of organocerium reagents to α‐alkoxy hydrazones. The results depend upon the organocerium reagents, the nature of protection for the hydroxy group, and the solvents used. Contrary to Grignard reagents, organocerium reagents derived from Grignard reagents effectively add to α‐alkoxy hydrazones. In addition, a new type of elimination reaction of α‐alkoxy hydrazones to the corresponding nitriles by methyl chloroformate was found. This methodology is an efficient and potentially practical synthetic route to β‐hydroxy amines. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:65–72, 2000     

A facile synthetic route to (η-benzoyleyclopentadienyl) metal compounds

A reaction between cyclopentadienylsodium and ethyl benzoate in refluxing THF produces (benzoylcyclopentadienyl)sodium (4) in 70–80% yield. Subsequent treatment of 4 in ethanol solution with thallium ethoxide affords (benzoyleyclopentadienyl)thallium (3) in nearly quantitative yield. Reactions of 3 with Mn(CO)₅Br, Re(CO)₅Br, [Rh(CO)₂Cl]₂ or FeCl₂ lead to the respective η⁵-benzoylcyclopentadienyl derivatives of these metals, and demonstrate the utility of 3 in organometallic syntheses. Reactions of several of these organometallic ketones with cymantrenyllithium [(η⁵-C₅H₄Li)Mn(CO)₃] provide a useful new route to bimetallic compounds.     

Multichain copoly(α-amino acid). III. Multichain copoly(α-amino acid) prepared by the reaction of copoly(L-lysine γ-methyl-L-glutamate) with N-carboxy anhydride of β-benzyl L-aspartate

Graft copolymerization of N-carboxy anhydride of β-benzyl-L -aspartate onto copoly(L -lysine γ-methyl-L -glutamate) was carried out in N,N-dimethylformaide which contained 3 v/v% of dimethyl sulfoxide to obtain multi-N^ε-poly(β-benzyl-L -aspartyl)copoly(L -lysine γ-methyl-L gluta mate). The degree of polymerization of the branch chain attained was much influenced by the interval of the grafting sites of the copoly(L -lysine γ-methyl-L -glutamate). The solvent-induced two-step conformational transition of the multichain copoly(α-amino acid) was observed in the chloroform-dichloroacetic acid system at 25°C by the ORD technique. The stability of the α-helical conformation of the backbone polymer chain was decreased by the presence of poly(β-benzyl-L -aspartyl) branch chains that could form unstable α-helical conformations of opposite spirals.     

The crystal structure of tris (indenyl)uranium (β,β,β-trifluoroethanolate)

The title compound was obtained by reaction of the methyl tris(indenyl) uranium complex with trifluoroethanol. A crystal structure reveals that there are two symmetrically independent molecules in the unit cell. The coordination geometry about the uranium atom is a flattened tetrahedron with three π-bonded indenyl rings and one σ-bonded trifluoroethanol oxygen atom. The U---O bonds are remarkably short. The U---C distances indicate trihapto mode of bonding of the indenyl rings. Variation of the ligand X in the U(C₉H₇)₃X class of complexes would not affect the stereochemistry about the U atom.     

Deoxydative thiation of 3-substituted pyridine N-oxides with 4-methoxytoluene-α-thiol: A divergent route to pyridinethiols

Synthesis of 3-substituted 2-pyridinethiols was achieved by thiation of pyridine N-oxides with 4-methoxytoluene-α-thiol in the presence of diethylcarbamoyl chloride followed by cleavage of the resulting sulfides. The ease of substitution was shown to be affected by nucleophilicity of the N-oxide oxygen. Addition of zinc bromide to the reaction, a need for triethylamine, decreased most of the yield for thiation products but the formation of 3-methoxy-2-methoxybenzylthiopyridine was only improved. A plausible mechanism of the substitution, particularly β-thiation to the N-oxide function, is discussed compared with the regiochemistry observed in the reaction with diethoxyphosphoryl chloride instead of diethylcarbamoyl chloride. The debenzylation to pyridinethiol was also found to be dependent on the electron-density in the pyridine ring.     

Reaction of α,β-poly(N-hydroxyethyl)-DL-aspartamide with derivatives of carboxylic acids

Benzoic acid, acetylsalicylic acid, and 4-acetamidobenzoic acid have been covalently linked by ester bonds to α,β-poly(N-hydroxyethyl)-DL -aspartamide (PHEA), a water soluble and nontoxic polymer, in order to study PHEA as a drug carrier.