Ru-catalyzed cycloisomerizations of aromatic homo- and bis-homopropargylic alcohols effectively afford benzofurans isochromenes. These processes proved to be chemo- regioselective (5-, 6-endo cyclizations) derived from key Ru vinylidene intermediates. The presence an amine/ammonium base-acid pair is crucial for the catalytic cycle.

A novel tandem Ru-catalyzed carbene addition to terminal alkynes/insertion into CH bonds in alkynyl acetals, ethers, and amines has been accomplished under mild reaction conditions (see scheme; TMS=trimethylsilyl). This cascade provides an efficient approach form complex spiro fused bicyclic structures by 1,5- 1,6-hydride shift/cyclization sequences from vinylcarbene Ru intermediates. Detailed facts of importance specialist readers are published as ”Supporting Information”. Such documents...

The wizard of Os: Regioselective osmium-catalyzed 7-endo heterocyclization aromatic alkynols affords benzoxepines in good yields. proposed catalytic cycle involves the key formation osmium–vinylidene complexes via an alkynyl-hydride–osmium(IV) complex from starting alkynol. Detailed facts importance to specialist readers are published as ”Supporting Information”. Such documents peer-reviewed, but not copy-edited or typeset. They made available submitted by authors. Please note: publisher is...

RhIII-catalyzed tandem C–H allylation and oxidative cyclization of anilides with allyl carbonates in the presence a slight excess AgSbF6 salt Cu(OAc)2 as oxidant affords easy, economical access to important bioactive 2-methylindoles. The new reaction supports wide range functional groups on anilide substrate. A possible mechanism is proposed basis for its rational further development.

A novel class of N-doped cationic PAHs (polycyclic aromatic hydrocarbons) bearing the benzo[c,d]fluoranthene scaffold has been synthesized by Rh(III)-catalyzed double-oxidative annulation 2-arylbenzimidazoles with alkynes. The overall process involves a double C–N bond formation through C–H/N–H functionalization.The solid-state structures and electronic properties new were analyzed. These azapolycycles readily reduced in presence LiAlH4 or addition PhLi to give interesting phenyl...

Abstract A novel synthesis of 2‐vinyldihydropyrans and dihydro‐1,4‐oxazines (morpholine derivatives) from alkynals alkynones has been developed. The cyclizations require a mild generation catalytic ruthenium carbenes terminal alkynes (trimethylsilyl)diazomethane followed by trapping with carbonyl nucleophiles. Mechanistic aspects the new are discussed.

Pyridines can be efficiently synthesized by Ru(II)-catalyzed [2 + 2 2] cycloaddition of 1,6-diynes to alpha,omega-dinitriles or electron-deficient nitriles cocyclization alkynes and nitriles. The reactions with dinitriles seem likely proceed via ruthenacyclopentadiene intermediates the electron-poor azaruthenacyclopentadienes. reaction asymmetric affords 2,3,6-trisubstituted pyridines in good yield.

Functionalized bicyclic 1,3-cyclohexadienes can be easily prepared by a new cascade reaction which involves the Ru-catalyzed addition of acyclic alkenes to 1,6-diynes give (Z)-hexatrienes, followed pure thermal 6e-pi electrocyclization.

[reaction: see text]. A new approach to carbazoles and benzannulated by means of intramolecular dehydro Diels-Alder reactions ynamides is reported. By using this approach, benzo[b]-, tetrahydrobenzo[b]-, naphtho[1,2-b]-, naphtho[2,1-b]-, dibenzo[a,c]carbazoles have been prepared in moderate-to-good yields.

TFA-promoted exo carbocyclizations of nonterminal 7-alkynals gave good to excellent yields seven-membered cycloalkenones, a medium-sized functionalized ring present in natural products with relevant pharmacological properties. Nonterminal 5- and 6-alkynals also very the corresponding cyclopentenones cyclohexenones. On other hand, terminal 5-alkynals endo These can be considered as tandem alkyne hydration/aldol condensation processes.

Abstract Ruthenium‐catalyzed cycloisomerizations of aromatic homo‐ and bis‐homopropargylic amines/amides efficiently afford indoles, dihydroisoquinolines dihydroquinolines. These processes were regioselective (5‐ 6‐ endo cyclizations) on using key Ru vinylidene intermediates. The presence an amine/ammonium base‐acid pair increased the rate cyclization facilitated catalytic turnover.

A new ruthenium-catalyzed cyclization of ortho-(alkynyloxy)benzylamines to dihydro-1,3-benzoxazines is reported. The thought take place via the vinyl ruthenium carbene intermediates which are easily formed from [Cp*RuCl(cod)] and N2 CHSiMe3 . mild reaction conditions efficiency procedure allow easy preparation a broad range 2-vinyl-2-substituted 1,3-benzoxazine derivatives. Rearrangement an internal C(sp) in starting material into tetrasubstituted C(sp(3) ) atom final highly remarkable.

Abstract Benzazepines and benzodiazepines, benzofused seven‐membered N‐heterocycles, compose an important family of natural products pharmaceuticals. Although certainly effectives, classical synthetic methods these cyclic compounds involve methodologies that often require multistep procedures, with generation waste materials lack sustainability. By contrast, cycloadditions based on transition metal catalyzed C−H bond activations (oxidative annulations) have emerged as appealing strategies...

2-Propynyldiarylacetylenes undergo thermal intramolecular [4 + 2] cycloaddition to give benzo[b]fluorene derivatives in good yields. The hybridization of the tether connecting reacting alkynes has a pronounced effect on course reaction. Theoretical calculations and isotopic labeling studies support mechanism which involves generation cyclic allene intermediate that evolves final benzo[b]fluorene.

The formation of complex polycyclic systems from terminal alkynes based on the concept pericyclic reactions catalytic metal-vinylidenes is presented. Metal-vinylidenes, easily formed with amounts several metal complexes, can be used in electrocyclizations, cycloadditions or sigmatropic rearrangements to afford valuable compounds.

Cycloalkenes can be efficiently prepared by a new Ru-catalyzed cyclization of terminal alkynals. Under appropriate conditions, cycloisomerizations to conjugated aldehydes may observed. Both processes involve catalytic Ru vinylidenes.

Abstract A novel osmium‐catalyzed cyclization of o ‐alkynyl phenethylamines to give 3‐benzazepines is reported. The procedure allows the straightforward preparation a broad range dopaminergic 3‐benzazepine derivatives. Mechanistic investigations revealed that process takes place via osmacyclopropene intermediates, which were isolated and characterized by X‐ray crystallography.

The first Pd-catalyzed [5 + 2] rollover annulation of 1-benzylpyrazoles with alkynes to assemble 10H-benzo[e]pyrazolo[1,5-a]azepines (tricyclic 2-benzazepines) has been developed. implies a twofold C-H activation aryl and heteroaryl Csp2-H bonds (C-H/C-H) (five-atom partners) give the annulated compounds.

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTOne-Step Synthesis of Symmetrical 3,3'-Substituted 2,2'-Bipyridine Ligands by Cobalt(I)-Catalyzed [2 + 2 2] CycloadditionsJesús A. Varela, Luis Castedo, and Carlos SaáView Author Information Departamento de Química Orgánica y Unidad Asociada al CSIC, Facultad Universidad Santiago Compostela 15706 Compostela, Spain Cite this: J. Am. Chem. Soc. 1998, 120, 46, 12147–12148Publication Date (Web):November 6, 1998Publication History Received10...

Cocyclization of 4-ethynyl-3-indoleacetonitriles with alkynes in the presence CpCo(CO)2 gives rise to ergoline derivatives 6-9, two which were transformed into racemic lysergene and LSD, respectively.

Thermal cyclization of 1-[2-(arylethynyl)phenyl]-3-trimethylsilylpropynones affords a mixture benzo[b]fluorenones and benzo[c]fluorenones. The ratio the two isomers can be efficiently varied between 100:0 0:100 by introducing substituents with appropriate electronic steric properties on aryl rings using an solvent.

Indoles, dihydroisoquinolines, and dihydroquinolines were efficiently prepared by ruthenium-catalyzed heterocyclizations of aromatic­ homo- bis-homopropargyl amines/amides in the presence an amine/ammonium base-acid pair. These regioselective 5-<i>endo</i> 6-<i>endo</i> cyclizations most probably occur nucleophilic trapping key ruthenium-vinylidene intermediates.