BINAP-CuH-catalysed enantioselective allylation using alkoxyallenes to access 1,2-,-diols.

Herein, we present an economical method for highly enantioselective and diastereoselective Cu-BINAP-catalysed reductive coupling of alkoxyallenes with a range of electronically and structurally diverse ketones to afford 1,2-,-diols, using PMHS as the hydride source. This reductive coupling has also been efficiently employed in the enantioselective desymmetrization of prochiral cyclic ketones harboring quaternary centres, in high yields with exclusive diastereoselectivity. Density Functional Theory (DFT) calculations are used to elucidate that the reaction is facilitated by a kinetically favourable "open" -enolate copper-alkoxyallene conformer, occurring at a lower Gibbs free energy barrier (by 3.

Pd-catalyzed -/-C-H-annulation of biphenyl amines with enynes through non-rollover cyclometallation.

Annulations through dual C-H activation represent a powerful tool to selectively assemble multi-cyclic scaffolds. We present herein a palladium-catalyzed -/-C-H-annulation of biphenyl amines with 1,6-enynes. This regioselective non-rollover cyclometallation was achieved through meticulous tuning of electronic factors of both the partners.

NHC-Catalyzed Umpolung Driven Intramolecular Cyclizations for the Generation of 3,4-Cycloheptanone Annulated Tetracyclic Indole Derivatives.

In this Letter, we disclose the development and exploitation of umpolung reactivity of N-heterocyclic carbene (NHC) organocatalysts in generating tetracyclic indole derivatives with the introduction of a cycloheptane ring forming event. The NHC-catalyzed intramolecular vinylogous Stetter, Stetter, benzoin, and formal cross-dehydrogenative coupling transformations have been executed, enabling the construction of 3,4-cycloheptannulated indole derivatives in good to excellent yields. The developed protocols utilize an inexpensive catalyst and feature operational simplicity, atom economy, gram-scale syntheses, and postsynthetic availability.

Organocatalytic enantioselective desymmetrization of enal-tethered cyclohexane-1,3-diones.

Organocatalytic asymmetric desymmetrization of prochiral cyclohexane-1,3-diones has been demonstrated through the merging of iminium and enamine activation. The tandem annulation reaction proceeds through a sequential oxa-Michael addition/intramolecular aldol reaction/[1,3]-amino oxetane rearrangement pathway. Mechanistic study using an O-water experiment suggests oxetane rearrangement instead of direct dehydration.

Pd-Catalyzed Chelation-Assisted Regioselective and Site Selective Cyclative C-H Annulation of Alkynyl Oximes with Activated Alkynes.

Electrophilic cyclization and concomitant C-H annulation constitute an expedient cascade strategy for the construction of multicyclic scaffolds with precise substitutional patterns. We report here a novel Pd-catalyzed cyclative annulation of ynone oxime with activated alkynes. The cascade features a dual regioselectivity including site selective C-H activation and chelation-assisted selective insertion of alkynes.

Pd-Catalyzed Vicinal Intermolecular Annulations of Iodoarenes, Indoles, and Carbazoles with Enynes.

Reaching the formidable C-H corners has been one of the top priorities of organic chemists in the recent past. This prompted us to disclose herein a vicinal annulation of 2-iodo benzoates, indoles, and carbazoles with N-embedded 1,6-enynes through 7-/8-membered palladacycles. The relay does not require the assistance of any directing group, leading to multicyclic scaffolds, which are readily diversified to an array of adducts (with new functional tethers and/or three contiguous stereocenters), in which we showcase a rare benzylic mono-oxygenation.

Rh(II)-Catalyzed Selective C(sp)-H Bond Electrophilic Amination of Aryl Azide-Tethered 1,3-Dicarbonyl Compounds.

Herein, we report the accomplishment of Rh(II)-catalyzed intramolecular amination of aryl azide-tethered 1,3-dicarbonyls to access privileged heterocyclic scaffolds with exclusive diastereoselectivity under simple reaction conditions. This method also allows an unconventional direct α-amination at electron-deficient C(sp)-H bonds of aryl azide-tethered 1,3-diketones to afford fused 2-azatricyclo[4.4.

Rh-catalyzed chemo-, stereo- and regioselective C-H cascade annulation of indolyloxopropanenitriles for pyranoindoles.

Selective annulations of alkynes represent a powerful tool for constructing multicyclic scaffolds while installing desired substitution patterns with precision. Herein, we report a Rh-catalyzed unique annulation of indolyl oxopropanenitrile with hydroxy-alkynoates to access pyranoindole cyclic motifs, featuring enol oxygen as a rare chemoselective reactive terminal. The reaction proceeds a five-membered oxy-rodacycle through C-H activation by a rhodium complex guided by enolic- and propargyloxy dual co-ordination to enable a regio- and stereoselective modular assembly.

Pd-catalyzed regioselective rollover dual C-H annulation cascade: facile approach to phenanthrene derivatives.

Annulations of unsaturated systems through C-H activation represent a powerful tool for producing multicyclic scaffolds. Having coordinating centers in both annulation partners (a dual coordination strategy) would afford remarkable selectivities in the outcomes. Along this concept, we report herein a Pd-catalyzed regioselective rollover cascade dual C-H annulation of -arylphenols with alkynols for constructing phenanthrene scaffolds.

Design and development of intramolecular doubly vinylogous Michael addition to access 3-aryl substituted 2-alkenyl-benzofurans and -indoles.

Herein, we have disclosed a rare example of an intramolecular doubly vinylogous Michael addition (DVMA). The reaction design exploits the innate reactivity of -heteroatom substituted -quinone methide (-QM) derivatives. The sequential reaction of -QMs and activated allyl halides proceeds through heteroatom-allylation, DVMA and oxidation to furnish a diverse range of 2-alkenyl benzofuran and 2-alkenyl indole derivatives in high yields.

One-pot domino synthesis of five- and six-membered fused dihydropyridines promoted by PPh-NBS in aqueous medium.

A facile one-pot synthesis of five- and six-membered fused dihydropyridines such as chromenodihydropyridines, pyrazolodihydropyridines and isoxazolopyridines was accomplished for the first time by employing PPh-NBS a formal [3 + 2 + 1] cycloaddition of 1,3-bisnucleophiles (, 2-aminochromone, 4-aminochromone, 5-aminopyrazole and 5-aminoisoxazole), β-enaminones and aldehydes in aqueous medium. The present approach involves a Michael type addition followed by intramolecular cyclization leading to the formation of two new C-C bonds and one C-N bond. High compatibility and excellent yields are the advantages of this protocol.

CuH-Catalyzed Enantioselective Desymmetrization of Cyclic 1,3-Diketones.

Herein, we report a CuH-catalyzed asymmetric desymmetrization of prochiral cyclopentane-1,3-diones to access cyclic 3-hydroxy ketones having an all-carbon quaternary center with high diastereoselectivity via hydrosilylation using PMHS as an inexpensive hydride source. This reaction displays high functional group tolerance including reducible alkyne, alkene, and ester groups with a broad substrate scope. The importance of chiral cyclic 3-hydroxy ketone building blocks was also demonstrated through the synthesis of (-)-estrone, the toxicodenane E core, and fused indoles.

Sequential One-Pot Carbene-Catalyzed Intramolecular Stetter Reaction and Acid-Mediated Condensation: Access to Heteroatom Analogues of π-Extended Polyaromatic Hydrocarbons.

In this Letter, we disclose a simple and effective method to access a variety of phenanthro[9,10-]furan and 1-dibenzo[,]indole derivatives based on the design of a carbene-catalyzed intramolecular Stetter reaction followed by a Paal-Knorr reaction in one-pot. These compounds are a class of π-extended polycyclic aromatic hydrocarbon (PAH) derivatives containing an oxygen/nitrogen atom. The practical utility of the developed transformation was demonstrated on the gram scales and postsynthetic transformations thereof.

Cu-Catalyzed tandem cyclization and coupling of enynones with enaminones for multisubstituted furans & furano-pyrroles.

A synthetic strategy that efficiently constructs complex molecular diversity in a few steps will always be embraced by organic chemists. Here, we report a cascade reaction of enynones with enaminones carbene insertion and aryl migration to engineer distinctive multisubstituted furans with an all-carbon quaternary center, and could extend the protocol in the same pot towards furano-pyrrole bis-heterocycles. Heterogeneity of this protocol was proved with the upshot of divergent chemical space under a relatively mild reaction environment.

Rhodium-Catalyzed Coordination-Assisted Regioselective and Migratory Three-Point Double Annulation of -Alkenyl Phenols with Tertiary Propargyl Alcohols.

We disclose herein a Rh(III)-catalyzed migratory three-point double annulation of -alkenyl phenols with propargyl alcohols for de novo construction of naphtho furan derivatives in a regio- and chemoselective manner. The protocol orchestrates two new rings with four new bonds in one operation without the need for any additive. Necessary labeled and control experiments are conducted to elucidate the reaction mechanism.

Palladium-Catalyzed Carbo-Aminative Cyclization of 1,6-Enynes: Access to Napthyridinone Derivatives.

1,6-Enynes have recently stimulated enormous attention toward paving the way to unique cascade cyclizations offering complex cyclic motifs from linear substrates. We describe herein a general approach to napthyridinones via the Pd-catalyzed annulation of 1,6-enynes with 2-iodoanilines. This protocol represents a rare carbo-aminative annulative cyclization via the 6-endo-trig mode, subduing the well-documented exo-trig/dig cyclizations.

Enantioselective Cu(I)-catalyzed borylative cyclization of enone-tethered cyclohexadienones and mechanistic insights.

The catalytic asymmetric borylation of conjugated carbonyls followed by stereoselective intramolecular cascade cyclizations with in situ generated chiral enolates are extremely rare. Herein, we report the enantioselective Cu(I)-catalyzed β-borylation/Michael addition on prochiral enone-tethered 2,5-cyclohexadienones. This asymmetric desymmetrization strategy has a broad range of substrate scope to generate densely functionalized bicyclic enones bearing four contiguous stereocenters with excellent yield, enantioselectivity, and diastereoselectivity.

Steric- and Electronic-Controlled Intramolecular [2 + 2]-Cycloaddition of Cyclohexadienone-Containing 1,7-Enynes.

Herein we have developed the silver-catalyzed electronic- and steric-controlled intramolecular formal [2 + 2]-cycloaddition of alkyne-tethered cyclohexadienones. Substrates with electron-rich alkynes and a less hindered quaternary carbon center afford tricyclic fused cyclobutenes through 1,7-enyne cyclization. In contrast, the formation of dihydrofurans was observed from electron-deficient alkynes via proton abstraction/C-O bond cleavage.

Rhodium-Catalyzed Regioselective Double Annulation of Enaminones with Propargyl Alcohols: Rapid Access to Arylnapthalene Lignan Derivatives.

We present here a rhodium-catalyzed oxidative three-point double annulation of enaminones with propargylic alcohols via a C-H and a C-N bond activation to access arylnaphthalene-based lignan derivatives. The key step in the reaction is the regioselective insertion of propargylic alcohol into the rhoda-cycle, a result of hydroxyl rhodium coordination. Necessary control experiments and KIE studies were conducted to determine the mechanism.

Rhodium-Catalyzed Annulation of Phenacyl Ammonium Salts with Propargylic Alcohols via a Sequential Dual C-H and a C-C Bond Activation: Modular Entry to Diverse Isochromenones.

Given their omnipresence in natural products and pharmaceuticals, isochromenone congeners are one of the most privileged scaffolds to synthetic chemists. Disclosed herein is a dual (/) C-H and C-C activation of phenacyl ammonium salts (acylammonium as traceless directing group) toward annulation with propargylic alcohols to accomplish rapid access for novel isochromenones by means of rhodium catalysis from readily available starting materials. This operationally simple protocol features broad substrate scope and wide functional group tolerance.

Tandem copper catalyzed regioselective -arylation-amidation: synthesis of angularly fused dihydroimidazoquinazolinones and the anticancer agent TIC10/ONC201.

Herein, we present a copper-catalyzed tandem reaction of 2-aminoimidazolines and -halo(hetero)aryl carboxylic acids that causes the regioselective formation of angularly fused tricyclic 1,2-dihydroimidazo[1,2-]quinazolin-5(4)-one derivatives. The reaction involved in the construction of the core six-membered pyrimidone moiety proceeded regioselective -arylation-condensation. The presented protocol been successfully applied to accomplish the total synthesis of TIC10/ONC201, which is an active angular isomer acting as a tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL): a sought after anticancer clinical agent.

Stereoselective synthesis of ()-1,3-bis(α,β-unsaturated carbonyl)-isoindolines from aldehydes and phenacyl azides under metal free conditions.

Here in the present manuscript, we report our observation of an unprecedented stereoselective synthesis of 2-isoindolin-1,3-ylidenes from 2-(formylphenyl)acrylates and phenacylazide in the presence of piperidine. Unlike in our previous findings, in which we accessed 3-keto-isoquinolines from the same starting materials under slightly modified reaction conditions, this unexpected one-pot tandem reaction allows an efficient and simple method to access a variety of highly functionalized ethyl ()-2-(()-3-(2-oxo-2-arylethylidene)-2,3-dihydro-1-benzo[]isoindol-1-ylidene)-acetates in very good to excellent yields (up to 91%). The present methodology is compatible with a wide variety of functional groups.

Visible-Light-Induced Deaminative Alkylation/Cyclization of Alkyl Amines with -Methacryloyl-2-phenylbenzoimidazoles in Continuous-Flow Organo-Photocatalysis.

Herein, we present a metal-free visible-light-induced eosin-y-catalyzed deaminative strategy for the sequential alkylation/cyclization of -methacryloyl-2-phenylbenzoimidazoles with alkyl amine-derived Katritzky salts, which provides an efficient avenue for the construction of various benzo[4,5]imidazo[2,1-]isoquinolin-6(5)-one derivatives in moderate to excellent yields under mild reaction conditions. The key enabling feature of this novel reaction includes utilization of redox-active pyridinium salts from abundant and inexpensive primary amine feedstocks that were converted into alkyl radicals via C-N bond scission and subsequent alkylation/cyclization with -methacryloyl-2-phenylbenzoimidazoles by the formation of two new C-C bonds. In addition, we implemented this protocol for a variety of amino acids, affording the products in moderate yields.

Harnessing Rhodium-Catalyzed C-H Activation: Regioselective Cascade Annulation for Fused Polyheterocycles.

In the realm of transition-metal catalyzed arene functionalization, rhodium(III) catalysis is considered as exemplary due to its propensity to activate C-H bonds to obtain comprehensive molecular assembly. Herein, we demonstrate a new rhodium(III) catalyzed assembly of polyheterocyclic scaffolds via C-H activation and regioselective annulation of 4-arylbut-3-yn-1-amines with 4-hydroxy-2-alkynoates. Heterocyclization and trans-metalation prior to annulation is the key for initiation of this relay redox-neutral catalytic cascade.

Design, synthesis and application of spiro[4.5]cyclohexadienones one-pot sequential -hydroxybenzylation/oxidative dearomatization.

One-pot sequential p-hydroxybenzylation/oxidative dearomatization/spiroannulation has been designed for the efficient construction of tetrahydrofuran containing spiro-cyclohexadienones. This reaction proceeds through the p-hydroxybenzylation of 1,3-diketones with p-hydroxybenzyl alcohol via quinone methide formation followed by oxidative dearomatization/spiroannulation with suitable alcohols. The Friedel-Crafts alkylation of spiro[4.