lactam synthesis by intramolecular ene insertion of acylazocarboxylates

Acylazocarboxylates having γ,δ or δ,ε unsaturation are generated by MnO₂ oxidation of the corresponding hydrazines. Internal ene reaction occurs at room temperature to give 5- or 6-membered lactam derivatives.     

Solventless lactam synthesis by intramolecular cyclizations of alpha-iminoester derivatives under microwave irradiation

We have previously reported a new synthesis of amides from esters and amines under microwave irradiation, offering much higher yields than those achieved with conventional heating [1]. We have now extended these studies to the ring closure of neat iminoesters I2, I3 and I4-I6 to give five- and six-membered ring lactams L5, L6 and larger lactams L7-L9 (where I means imine and L means lactam), respectively, under both classical heating conditions and microwave irradiation.     

Novel eta 3 -1-silaallyl tungsten complexes via Si-H bond activation of hydrovinylsilanes: structure and reactivity toward methanol

Reactions of cis-Cp*(CO)2W(MeCN)Me (1) with HSiMe2(CH=CR2) (R = H, Me) afford the novel eta3-1-silaallyl complexes Cp*(CO)2W(eta3-Me2SiCHCR2) [R = H (2), Me (3)] accompanied by liberation of MeCN and CH4 via thermal Si-H bond activation. eta3-Coordination and exo conformation of the 1-silaallyl ligand in 3 are shown by X-ray crystal analysis, which reveals the partial double bond character of the Si-C bond (1.800(4) A) in the silaallyl moiety. Complexes 2 and 3 show extremely high reactivity toward MeOH to give the hydrido-(methoxysilyl)alkene complex trans-Cp*(CO)2WH(eta2-MeOMe2SiCH=CH2) (4) and the four-membered metallacycle Cp*(CO)2WCH(CHMe2)SiMe2OMe (6), respectively.     

Novel synthesis of lactam from alkyne having amide in a tether using fischer chromium carbene complex

A novel lactam synthesis from alkyne having amide in a tether was developed. The reaction proceeds via a vinylketene complex generated from alkyne and Fischer chromium carbene complex, and the lactam ring was formed from carbon monoxide, alkyne carbon and nitrogen of tosylamide. The four-,five-, six-, and seven-membered lactams having a substituent at the -position were obtained in good yields.     

Novel synthesis of medium-sized oxa-heterocycles by palladium-catalyzed intramolecular Heck reaction

An efficient and high yielding method for the synthesis of eight-membered heterocyclic skeletons has been developed via palladium-catalyzed intramolecular Heck reaction.     

A dicoordinate palladium(0) complex with an unusual intramolecular eta(1)-arene coordination

The reaction of (tmeda)PdMe2 with dcpBiph gives (dcpBiph)2Pd in high yield. The solid-state structure of (dcpBiph)2Pd reveals a bent P-Pd-P framework and an unusual eta1-arene interaction between the palladium and the distal ring of one of the biphenyl substituents. In solution, an additional conformer exists which does not show a pi-interaction with a biphenyl ring. The low-coordinate complex, (dcpBiph)2Pd, undergoes C-X oxidative addition reactions with PhX (X = I, Br, Cl). A minor product resulting from metalation of the biphenyl ring is also observed.     

Studies toward the synthesis of roseophilin: lactam formation and Wittig/aldol methodology

In this communication, we introduce our retrosynthetic approach to the synthesis of roseophilin. An interesting, new Wittig/aldol methodology is described. Also discussed is macrocyclization of an azide acid to form an unsaturated lactam.     

Novel synthesis of cinnolines and 1-aminoindolines via Cu-catalyzed intramolecular N-arylation of hydrazines and hydrazones prepared from 3-haloaryl-3-hydroxy-2-diazopropanoates

A new and facile access to cinnolines, dihydrocinnolines, and 1-aminoindolines was established by use of diazo functionalities. The hydrazines and hydrazones as cyclization precursors derived from 3-haloaryl-3-hydroxy-2-diazopropanoates, which are prepared by one-pot procedure utilizing phase-transfer catalysis, are successfully converted to the corresponding nitrogen heterocycle by Cu-catalyzed N-arylation. Furthermore, analysis of UV spectra proved that 4-oxo-3-carboxylates predominantly exist not as 4-hydroxycinnoline (enol form) but as cinnolone (keto form).     

Dynamic equilibration of eta 1-carbene and eta 2-alkyne moieties within an alkynylcarbene dimanganese complex

The coordination of an additional [Cp(CO)2Mn] fragment to the alkyne linkage of an alkynylcarbene complex of the type Cp(CO)2Mn=C(R')C identical to CR" yields a highly fluxional molecule, in which the [eta 1-carbene] and [eta 2-alkyne] moieties are seen to exchange rapidly on the NMR time scale.     

Studies toward the total synthesis of (+)-gelsemine and synthesis of spirocyclopentaneoxindole through intramolecular Michael cyclization

During the approach to the total synthesis of (+)-gelsemine, two novel spirocyclopentaneoxindole compounds 2 and 3 were obtained. Starting from compound 9, spirocyclopentaneoxindole 3 was efficiently and unexpectedly obtained through a Boc migration-intramolecular Michael cyclization cascade procedure. This intramolecular Michael addition strategy allows conveniently access to complex spirooxindole and spirocyclopentaneoxindole derivatives.     

A post-Ugi carbonylation/intramolecular amidation approach toward the synthesis of macrolactams

An Ugi-deprotection-carbonylation/intramolecular amidation approach toward the synthesis of novel bicyclic and tricyclic macrolactams is described.     

Convenient synthesis of 3-alkoxy-3-aryloxindoles by intramolecular arylation of mandelic amides

Medicinally important 3-alkoxy-3-aryloxindoles are conveniently prepared by the rapid microwave-promoted palladium-catalyzed intramolecular enolate arylation of mandelate-derived anilides.     

Novel eta1-N,eta2-C,C-binding mode between pyridinyl-functionalized cyclopentadienyl ligands and iridium

The reaction between 2-(2,3,4,5-tetramethyl-cyclopenta-1,3-dienyl)-pyridine 1 and IrCl3 was performed in an attempt to synthesize a cyclometalated system with decreased pi conjugation in the ligand. An unexpected reduction and rearrangement of bis-pyridinyl-cyclopentadienyl cyclometalated Ir(III) intermediate 2 took place yielding bis-pyridinyl-fulvene Ir(I) complex 4, which exhibits a novel bis-eta1-N,eta2-C,C-binding mode between the pyridinyl-functionalized fulvene ligand and iridium. The iridium atom in 4 is not sandwiched between two cyclopentadienyl moieties; rather, the two cyclopentadienyl groups adopt a pi-pi stacking arrangement with a centroid-centroid distance of 3.494 A. The Cl/P(wedge)O ligand-exchange reaction between 4 and 2-[(diphenylphosphanyl)-methyl]-1,1,1,3,3,3-hexafluoro-propan-2-ol 5 led to loss of one pyridinyl-functionalized fulvene ligand and produced complex 6, in which the remaining pyridinyl-functionalized fulvene ligand exhibits the mono-eta1-N,eta2-C,C-binding mode.     

Development of copper-mediated allylation of γ-activated-α,β-unsaturated lactam toward peptide mimetic synthesis

Reactions of γ-activated-α,β-unsaturated lactams with allylboronate in the presence of LiOi-Pr and CuX (stoichiometric or catalytic amount) proceed in an anti-S_N2′ manner to yield α-allylated compounds that serve as a potential synthetic intermediate for cis-aminoacyl-Pro mimetics.     

Palladium-catalyzed decarboxylation of allenyl 3-oxoalkanoates: an efficient synthesis of 3,4-allenyl ketones

An efficient synthesis of 3,4-allenyl ketones via the Pd-catalyzed decarboxylative coupling of the readily available 3-oxoalkanoates is reported. The C-C bond forming reaction occurs under mild conditions producing CO(2) as the only byproduct.     

Asymmetric synthesis of 3-methylthio alcohols by intramolecular Michael addition reactions

Chiral 3-methylthio alcohols have been synthesized through a known intramolecular sulfur transfer reaction that has been carried out in di- and trisubstituted α,β-unsaturated N-enoyl oxazolidinethiones as substrates, giving rise to syn/anti-diastereomers. The anti-diastereomer is favored and obtained via a highly diastereoselective protonation step.     

Activation of iron-coordinated arenes toward the attack of carbon,nitrogen, and oxygen nucleophiles

Functionally-substituted carbon nucleophiles undergo addition to arenes coordinated to positive iron, but nitrogen and oxygen nucleophiles abstract α protons from iron-coordinated methylated arenes.     

Novel intramolecular reactivity of oximes: synthesis of cyclic and spiro-fused imines

Under conventional heat (135-145 degrees C) or microwave irradiation and 1 equiv of acetic anhydride, ortho-substituted aryl-oximes undergo a novel sp3 C-H activated cyclization to produce the corresponding isoindoles, and aliphatic oximes afford the corresponding dihydropyrroles. The cyclization occurs with various substrates in good yield (46-82%) leading to unique spiro-fused and cyclic imines. An initial mechanistic investigation suggests the reaction occurs via a nitrenium or vinyl nitrene intermediate. [reaction: see text]     

Asymmetric addition of dimethylzinc to N-tosylarylimines catalyzed by a rhodium-diene complex toward the synthesis of chiral 1-arylethylamines

[STRUCTURE: SEE TEXT] A rhodium complex coordinated with a chiral diene, (R,R)-2,5-diphenylbicyclo[2.2.2]octa-2,5-diene (Ph-bod), catalyzed the asymmetric addition of dimethylzinc to N-tosylarylimines to give high yields of chiral 1-aryl-1-ethylamines with high enantioselectivity (94-98% ee).     

Copper-mediated intramolecular aza-Wacker-type cyclization of 2-alkenylanilines toward 3-aryl indoles

A copper-mediated intramolecular aza-Wacker-type cyclization was developed for the direct and efficient synthesis of 3-aryl indoles using 2-alkenylanilines in moderate to good yields with good functional group compatibility. This strategy shows the high efficiency, operational simplicity as well as broad substrate scope.