scispace - formally typeset
Search or ask a question

Showing papers on "Annulation published in 2016"


Journal ArticleDOI
TL;DR: The gold-catalyzed C-H annulation of anthranil derivatives with alkynes offers a facile, flexible, and atom-economical one-step route to unprotected 7-acylindoles and represents a versatile platform for the construction of diverse indolyl frameworks.
Abstract: The gold-catalyzed CH annulation of anthranil derivatives with alkynes offers a facile, flexible, and atom-economical one-step route to unprotected 7-acylindoles. An intermediate α-imino gold carbene, generated by an intermolecular reaction, promotes ortho-aryl CH functionalization to afford the target products. The transformation proceeds with a broad range of substrates under mild conditions. Moreover, the obtained functionalized indole products represent a versatile platform for the construction of diverse indolyl frameworks.

250 citations


Journal ArticleDOI
Yudong Yang1, Kaizhi Li1, Yangyang Cheng1, Danyang Wan1, Mingliang Li1, Jingsong You1 
TL;DR: An overview on emerging procedures, highlights their advantages and limitations, and covers the latest progress in the rapid synthesis of organic functional materials and natural products are offered.

235 citations


Journal ArticleDOI
TL;DR: The development of such a cooperative catalytic system dramatically expands the scope of NHC organocatalysis by opening up new metal-catalyzed reaction pathways for homoenolate intermediates.
Abstract: A combination of NHC organocatalysis and transition-metal catalysis gives rise to fundamentally new cooperative reactivity and enables the regio- and enantioselective annulation reaction between enals and vinyl benzoxazinanones. The cooperative umpolung annulation eliminates mutual deactivation and leads to a diverse set of benzazepine derivatives in good yields with excellent enantioselectivities (up to 99% ee). The development of such a cooperative catalytic system dramatically expands the scope of NHC organocatalysis by opening up new metal-catalyzed reaction pathways for homoenolate intermediates.

205 citations


Journal ArticleDOI
TL;DR: The first copper-catalyzed asymmetric decarboxylative [4 + 1] cycloaddition of propargylic carbamates and sulfur ylides was successfully developed and led to a series of chiral indolines with synthetically flexible alkyne groups in good yields and with high enantio- and diastereoselectivities.
Abstract: The first copper-catalyzed asymmetric decarboxylative [4 + 1] cycloaddition of propargylic carbamates and sulfur ylides was successfully developed. This strategy led to a series of chiral indolines with synthetically flexible alkyne groups in good yields and with high enantio- and diastereoselectivities (up to 99% yield, 98% ee, and >95:5 dr). A possible mechanism and stereoinduction mode with copper-allenylidenes were proposed as the possible dipolar intermediate.

185 citations


Journal ArticleDOI
TL;DR: In this article, an unprecedented formal [3 + 2] cycloaddition of para-quinone methides with vinyl epoxides/cyclopropanes is presented, which can deliver a wide range of spiro[4.5]decanes in high efficiency and stereoselectivity.
Abstract: Here, we present an unprecedented formal [3 + 2] cycloaddition of para-quinone methides with vinyl epoxides/cyclopropanes to deliver a wide range of spiro[4.5]decanes in high efficiency and stereoselectivity. The commercial availability of the catalysts and reagents, together with the convenient procedure, makes it an attractive method in asymmetric synthesis.

185 citations


Journal ArticleDOI
TL;DR: Four cobalt-catalyzed oxidative annulation reactions of nitrogen-containing arenes with alkynes proceeds by C-H activation, thus leading to biologically useful quaternary ammonium salts in high yields, comparable to those reactions catalyzed by rhodium and ruthenium complexes.
Abstract: Four cobalt-catalyzed oxidative annulation reactions of nitrogen-containing arenes with alkynes proceeds by C-H activation, thus leading to biologically useful quaternary ammonium salts, including pyridoisoquinolinium, cinnolinium, isoquinolinium, and quinolizinium salts, in high yields. The results are comparable to those reactions catalyzed by rhodium and ruthenium complexes. The transformation of the salts into various N-heterocycles has also been demonstrated.

177 citations


Journal ArticleDOI
TL;DR: A catalyst-controlled switch in the chemo- and diastereodivergent annulation reactions of Morita-Baylis-Hillman carbonates, derived from isatins and 2-alkylidene-1H-indenes-1,3(2H)-diones, in exclusive α-regioselectivity is presented, leading to a collection of compounds with skeletal and stereogenic diversity.
Abstract: Regulating both the chemo- and diastereoselectivity, divergently, of a reaction is highly attractive but extremely challenging. Presented herein is a catalyst-controlled switch in the chemo- and diastereodivergent annulation reactions of Morita-Baylis-Hillman carbonates, derived from isatins and 2-alkylidene-1H-indene-1,3(2H)-diones, in exclusive α-regioselectivity. α-Isocupreine efficiently catalyzed [2+1] reactions to access cyclopropane derivatives, and the diastereodivergent [3+2] annulations were accomplished by employing either a chiral phosphine or a DMAP-type molecule. All reactions exhibited excellent chemoselectivities, and good to remarkable stereoselectivities were furnished, thus leading to a collection of compounds with skeletal and stereogenic diversity. Moreover, DFT computational calculations elucidated the catalyst-based switch in mechanism.

175 citations


Journal ArticleDOI
TL;DR: This method offers a regiospecific and modular access to 2-aminoquinolines and other quinoline derivatives under mild conditions and with a broad functional-group tolerance.
Abstract: A gold-catalyzed cascade annulation of propargylic silyl ethers with anthranils proceeds through a sequential ring opening/1,2-H-shift/protodeauration/Mukaiyama aldol cyclization. This method offers a regiospecific and modular access to 2-aminoquinolines and other quinoline derivatives under mild conditions and with a broad functional-group tolerance. The conversion is possible on a gram scale, which underlines the synthetic practicability of this methodology. The versatility of the obtained scaffold has been demonstrated by useful postfunctionalization.

175 citations


Journal ArticleDOI
TL;DR: The [3+4] annulation strategy leads to the seven-membered target spiro heterocycles bearing an oxindole moiety in high yields and excellent enantioselectivities with a wide variety of substrates.
Abstract: A strategy for the NHC-catalyzed asymmetric synthesis of spirobenzazepinones, spiro-1,2-diazepinones, and spiro-1,2-oxazepinones has been developed via [3+4]-cycloaddition reactions of isatin-derived enals (3C component) with in-situ-generated aza-o-quinone methides, azoalkenes, and nitrosoalkenes (4atom components). The [3+4] annulation strategy leads to the seven-membered target spiro heterocycles bearing an oxindole moiety in high yields and excellent enantioselectivities with a wide variety of substrates. Notably, the benzazepinone synthesis is atroposelective and an all-carbon spiro stereocenter is generated.

144 citations


Journal ArticleDOI
TL;DR: The enantioselective synthesis of pyrazolone-fused spirocyclohexadienones was demonstrated by the reaction of α,β-unsaturated aldehydes with α-arylidene pyrazolinones under oxidative N-heterocyclic carbene (NHC)catalysis.
Abstract: The enantioselective synthesis of pyrazolone-fused spirocyclohexadienones was demonstrated by the reaction of α,β-unsaturated aldehydes with α-arylidene pyrazolinones under oxidative N-heterocyclic carbene (NHC)catalysis. This atom-economic and formal [3+3] annulation reaction proceeds through a vinylogous Michael addition/spiroannulation/dehydrogenation cascade to afford spirocyclic compounds with an all-carbon quaternary stereocenter in moderate to good yields and excellent ee values. Key to the success of the reaction is the cooperative NHC-catalyzed generation of chiral α,β-unsaturated acyl azoliums from enals, and base-mediated tandem generation of dienolate/enolate intermediates from pyrazolinones.

142 citations


Journal ArticleDOI
TL;DR: In this article, the redox-neutral annulation of alkynes by differently decorated nitrones set the stage for a step-economical access to indoles with ample substrate scope.
Abstract: The redox-neutral annulation of alkynes by differently decorated nitrones set the stage for a step-economical access to indoles with ample substrate scope. The redox-neutral C–H/N–O functionalization process proceeded through kinetically relevant C–H activation by carboxylate assistance, and displayed an excellent site- and regio-selectivity with unsymmetrical nitrones and alkynes.

Journal ArticleDOI
TL;DR: A highly diastereoselective method for the synthesis of dihydroepoxybenzofluorenone derivatives from aromatic/vinylic amides and bicyclic alkenes is described, for the first time that a [3+2] cycloaddition is described in this context.
Abstract: A highly diastereoselective method for the synthesis of dihydroepoxybenzofluorenone derivatives from aromatic/vinylic amides and bicyclic alkenes is described. This new transformation proceeds through cobalt-catalyzed C-H activation and intramolecular nucleophilic addition to the amide functional group. Transition-metal-catalyzed C-H activation reactions of secondary amides with alkenes usually lead to [4+2] or [4+1] annulation; to the best of our knowledge, this is the first time that a [3+2] cycloaddition is described in this context. The reaction proceeds under mild conditions and tolerates a wide range of functional groups. Mechanistic studies imply that the C-H bond cleavage may be the rate-limiting step.

Journal ArticleDOI
TL;DR: A highly enantioselective [3+2] cycloaddition reaction that makes use of isatin-derived ketimines as reaction partners was developed, and both simple and γ-substituted allenoates could be utilized.
Abstract: Phosphine-catalyzed enantioselective annulation reactions involving ketimines are a daunting synthetic challenge owing to the intrinsic low reactivity of ketimine substrates. A highly enantioselective [3+2] cycloaddition reaction that makes use of isatin-derived ketimines as reaction partners was developed. Notably, both simple and γ-substituted allenoates could be utilized, and various 3,2'-pyrrolidinyl spirooxindoles with a tetrasubstituted stereocenter were obtained in excellent yields and with nearly perfect enantioselectivity (>98 % ee in all cases).

Journal ArticleDOI
TL;DR: A novel [3 + 2] annulation between para-quinone methides and vinylcyclopropanes for the synthesis of spiro[4.5]deca-6,9-diene-8-ones has been described and the reaction exhibited good functional group tolerance and scalability.

Journal ArticleDOI
Zhuo-Zhuo Zhang1, Bin Liu1, Jing-Wen Xu1, Sheng-Yi Yan1, Bing-Feng Shi1 
TL;DR: A mild Co(III)-catalyzed oxidative annulation of N-arylureas and internal alkynes has been developed, providing a new opportunity for the synthesis of diverse indoles.

Journal ArticleDOI
TL;DR: A comprehensive review of the literature on DMSO-based Oxidations can be found in this article, where the authors systematically summarized synthetic transformations that have utilized the fragments of dimethyl sulfoxide as building blocks.
Abstract: Dimethyl sulfoxide is generally characterized as a solvent and oxidant rather than as a substrate, building block, or synthon in organic chemistry. However, an abundance of reports have recently appeared that demonstrate dimethyl sulfoxide acting in these roles. This review article offers a comprehensive summary of the literature on this topic until the end of 2015. Synthetic transformations that have utilized the ‘C–S–C’, ‘C’, and ‘C–S’ fragments of dimethyl sulfoxide as building blocks are systematically summarized. 1 Introduction 2 History and Recent Highlights of DMSO-Based Oxidations 3 DMSO-Based Methylthiomethylation (–CH2SMe) 4 DMSO as a One-Carbon Synthon 4.1 DMSO-Based Methylation (–Me) 4.2 DMSO-Based Methylenation (–CH2–) 4.3 DMSO-Based Annulation/Aromatization (=CH–) 4.4 DMSO-Based Formylation (–CHO) 4.5 DMSO-Based Cyanation (–CN) 5 DMSO as Synthon for ‘S–C’ Functionalities 5.1 DMSO-Based Thiomethylation (–SMe) 5.2 DMSO-Based Methylsulfonylation (–SO2Me) 6 Summary and Conclusions

Journal ArticleDOI
TL;DR: The synthesis of N-unprotected indoles has been realized via Rh(III)-catalyzed C-H activation/annulation of imidamides with α-diazo β-ketoesters through a rhodacyclic intermediate.

Journal ArticleDOI
TL;DR: This is the first example of a manganese-catalyzed C-H transformation using an oxygen-directing group and Triphenylborane played an important role in this reaction to cooperatively promote the annulation reaction.

Journal ArticleDOI
TL;DR: A green atom-economical method for the synthesis of highly functionalized 1-amino and 1-carbon substituted isoquinolines from the reaction of N′-hydroxybenzimidamides and aryl ketoximes, respectively, with alkynes via pentamethylcyclopentadienylcobalt(III)-catalyzed CH/NO bond activation is described in this paper.
Abstract: A green atom-economical method for the synthesis of highly functionalized 1-amino and 1-carbon substituted isoquinolines from the reaction of N′-hydroxybenzimidamides and aryl ketoximes, respectively, with alkynes via pentamethylcyclopentadienylcobalt(III)-catalyzed CH/NO bond activation is described. The external oxidant-free annulation reaction uses the =NOH moiety in N′-hydroxybenzimidamides or N-aromatic ketone oximes as the directing group and internal oxidant. This first row transition metal-catalyzed annulation serves as an efficient alternative for the synthesis of isoquinolines, as water is the only by-product and expensive noble metals such as rhodium(III), iridium(III), palladium(II), and ruthenium(II) are not required. The reaction proceeds via CH activation, alkyne insertion, reductive elimination, and NO activation.

Journal ArticleDOI
TL;DR: A new cobalt-catalyzed phenolic OH-assisted C–H functionalization of 2-vinylphenols with allenes to give various 2H-chromenes is described, which is the first time that allenes are used as the coupling partners in the cobalt–H activation reactions.
Abstract: A new cobalt-catalyzed phenolic OH-assisted C–H functionalization of 2-vinylphenols with allenes to give various 2H-chromenes is described. It is the first time that allenes are used as the coupling partners in the cobalt-catalyzed C–H activation reactions. In most cases, cobalt-catalyzed oxidative annulation of arenes with alkenes or alkynes via C–H activation gave [4 + 2] or [3 + 2] cyclization products, but the present catalytic reaction afforded an oxidative [5 + 1] cyclization products with the allenes acting as a one-carbon coupling partner. The catalytic reaction is proposed to proceed via the C–H activation of the vinyl group, allene insertion, and an unusual intramolecular regioselective phenoxide addition.

Journal ArticleDOI
TL;DR: The use of rhodium(III) complexes equipped with a suitable atropchiral cyclopentadienyl ligand, in conjunction with a carboxylic acid additive, enables an enantioselective and high yielding access to such spirocyclic sultams.
Abstract: Chiral spirocyclic sultams are a valuable compound class in organic and medicinal chemistry. A rapid entry to this structural motif involves a [3+2] annulation of an N-sulfonyl ketimine and an alkyne. Although the directing-group properties of the imino group for C-H activation have been exploited, the developments of related asymmetric variants have remained very challenging. The use of rhodium(III) complexes equipped with a suitable atropchiral cyclopentadienyl ligand, in conjunction with a carboxylic acid additive, enables an enantioselective and high yielding access to such spirocyclic sultams.

Journal ArticleDOI
TL;DR: The cyclization of substituted N-methoxy benzamides with alkynes in the presence of an easily affordable cobalt complex and NaOAc provides isoquinolone derivatives in good to excellent yields.
Abstract: The cyclization of substituted N-methoxy benzamides with alkynes in the presence of an easily affordable cobalt complex and NaOAc provides isoquinolone derivatives in good to excellent yields. The cyclization reaction is compatible with a range of functional group-substituted benzamides, as well as ester- and alcohol-substituted alkynes. The cobalt complex [Co(III) Cp*(OR)2 ] (R=Me or Ac) serves as an efficient catalyst for the cyclization reaction. Later, isoquinolone derivatives were converted into 1-chloro and 1-bromo substituted isoquinoline derivatives in excellent yields in the presence of POCl3 or PBr3 .

Journal ArticleDOI
TL;DR: Cp*-free cobalt-catalyzed alkyne annulations by C-H/N-H functionalizations were accomplished with molecular O2 as the sole oxidant, providing step-economical access to the anticancer topoisomerase-I inhibitor 21,22-dimethoxyrosettacin.
Abstract: Cp*-free cobalt-catalyzed alkyne annulations by C-H/N-H functionalizations were accomplished with molecular O2 as the sole oxidant. The user-friendly oxidase strategy proved viable with various internal and terminal alkynes through kinetically relevant C-H cobaltation, providing among others step-economical access to the anticancer topoisomerase-I inhibitor 21,22-dimethoxyrosettacin. DFT calculations suggest that electronic effects control the regioselectivity of the alkyne insertion step.

Journal ArticleDOI
Peng Sun1, Shang Gao1, Chi Yang1, Songjin Guo1, Aijun Lin1, Hequan Yao1 
TL;DR: A Rh(III)-catalyzed annulation between salicylaldehydes and diazo compounds with controllable chemoselectivity is described, which exhibited good functional group tolerance and scalability.

Journal ArticleDOI
TL;DR: An efficient Rh(III)-catalyzed synthetic method for indoloquinoline derivatives from readily available indoles and isoxazoles was developed and a catalytically competent five-membered rhodacycle has been isolated and characterized, thus revealing a key intermediate in the catalytic cycle.

Journal ArticleDOI
TL;DR: A new cobalt(II)-catalyzed decarboxylative C-H activation/annulation of benzamides and alkynyl carboxylic acids has been described, which enables a switchable cyclization to isoquinolones and isoindolinones with excellent selectivity.

Journal ArticleDOI
Shanping Chen1, Yuxia Li1, Penghui Ni1, Huawen Huang1, Guo-Jun Deng1 
TL;DR: An efficient indole-to-carbazole strategy has been developed under metal-free conditions that conveniently enabled the assembly of a large number of diversified carbazole products with good tolerance of a broad range of functional groups.

Journal ArticleDOI
TL;DR: A catalytic asymmetric total synthesis of (-)-actinophyllic acid is described, with the key step being a chiral phosphine-catalyzed [3 + 2] annulation between an imine and an allenoate to form a pyrroline intermediate in 99% yield and 94% ee.
Abstract: Described herein is a catalytic asymmetric total synthesis of (-)-actinophyllic acid, with the key step being a chiral phosphine-catalyzed [3 + 2] annulation between an imine and an allenoate to form a pyrroline intermediate in 99% yield and 94% ee. The synthesis also features CuI-catalyzed coupling between a ketoester and a 2-iodoindole to shape the tetrahydroazocine ring; intramolecular alkylative lactonization; SmI2-mediated intramolecular pinacol coupling between ketone and lactone subunits to assemble the complex skeleton of (-)-actinophyllic acid; and an unprecedented regioselective dehydroxylation.

Journal ArticleDOI
Yuanbin Zhang1, Yuji Sun1, Furong Lin1, Jiyong Liu1, Simon Duttwyler1 
TL;DR: 1,2,3-Trisubstituted closo-dodecaborates with B-O, B-N, and B-C bonds as well as a fused borane oxazole ring have been synthesized by rhodium-catalyzed direct cage B-H alkenylation and annulation of ureido boranes in the first reported example of regioselective B- H bond functionalization of the [B12
Abstract: 1,2,3-Trisubstituted closo-dodecaborates with B−O, B−N, and B−C bonds as well as a fused borane oxazole ring have been synthesized by rhodium-catalyzed direct cage B−H alkenylation and annulation of ureido boranes in the first reported example of regioselective B−H bond functionalization of the [B12H12]2− cage by transition-metal catalysis. This reaction proceeded at room temperature under ambient conditions and exhibited excellent selectivity for efficient monoalkenylation with good functional-group tolerance. The urea moiety enabled B−H activation by acting as a directing group, was incorporated in the oxazole ring in situ, and also avoided multiple alkenylation. A possible mechanism is proposed on the basis of the isolation of a rhodium agostic intermediate and control experiments.

Journal ArticleDOI
TL;DR: The unprecedented annulation reaction successfully facilitated the construction of sp(3) -rich and highly substituted 3,2'-pyrrolidinyl spirooxindoles supporting many chiral centers.
Abstract: Catalytic addition of chiral phosphine, that is, (R)- or (S)-SITCP, to an α-substituted allene ester generated a zwitterionic dipole. Under optimized reaction conditions, this dipole could engage isatine-derived N-Boc-ketimines in a novel mode of [3+2] annulation reaction. Pyrrolinyl spirooxindoles are thus afforded in high yields and with excellent enantioselectivities. The unprecedented annulation reaction successfully facilitated the construction of sp(3) -rich and highly substituted 3,2'-pyrrolidinyl spirooxindoles supporting many chiral centers.