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Rhodium(III)-catalyzed dearomatizing (3 + 2) annulation of 2-alkenylphenols and alkynes.

ABSTRACT: Appropriately substituted 2-alkenylphenols undergo a mild formal [3C+2C] cycloaddition with alkynes when treated with a Rh(III) catalyst and an oxidant. The reaction, which involves the cleavage of the terminal C-H bond of the alkenyl moiety and the dearomatization of the phenol ring, provides a versatile and efficient approach to highly appealing spirocyclic skeletons and occurs with high selectivity.

SUBMITTER: Seoane A

PROVIDER: S-EPMC4077242 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Divergent rhodium-catalyzed electrochemical vinylic C-H annulation of acrylamides with alkynes.

Project description:α-Pyridones and α-pyrones are ubiquitous structural motifs found in natural products and biologically active small molecules. Here, we report an Rh-catalyzed electrochemical vinylic C-H annulation of acrylamides with alkynes, affording cyclic products in good to excellent yield. Divergent syntheses of α-pyridones and cyclic imidates are accomplished by employing N-phenyl acrylamides and N-tosyl acrylamides as substrates, respectively. Additionally, excellent regioselectivities are achieved when using unsymmetrical alkynes. This electrochemical process is environmentally benign compared to traditional transition metal-catalyzed C-H annulations because it avoids the use of stoichiometric metal oxidants. DFT calculations elucidated the reaction mechanism and origins of substituent-controlled chemoselectivity. The sequential C-H activation and alkyne insertion under rhodium catalysis leads to the seven-membered ring vinyl-rhodium intermediate. This intermediate undergoes either the classic neutral concerted reductive elimination to produce α-pyridones, or the ionic stepwise pathway to produce cyclic imidates.

| S-EPMC7876044 | biostudies-literature

Annulation of Hydrazones and Alkynes via Rhodium(III)-Catalyzed Dual C-H Activation: Synthesis of Pyrrolopyridazines and Azolopyridazines.

Project description:Hydrazones readily synthesized from N-aminopyrroles or N-aminoazoles and aldehydes undergo Rh(III)-catalyzed dual C-H activation and coupling with aryl- and alkyl-substituted alkynes to give pyrrolopyridazines or azolopyridazines, respectively. This transformation represents a rare example of hydrazoyl C-H activation and proceeds without heteroatom functionality to direct C-H activation. Hydrazones derived from aromatic, alkenyl, and aliphatic aldehydes were effective inputs, and tethering the alkyne to the hydrazone enabled annulations to more complex, tricyclic products.

| S-EPMC7007857 | biostudies-literature

Intermolecular [5+2] Annulation between 1-Indanones and Internal Alkynes by Rhodium-Catalyzed C-C Activation.

Project description:Herein, we report a [5+2] cycloaddition between readily accessible 1-indanones and internal alkynes through Rh-catalyzed activation of less strained C-C bonds. The reaction is enabled by a strongly σ-donating NHC ligand and a carefully modified temporary directing group. A wide range of functional groups is tolerated, and the method provides straightforward access to diverse benzocycloheptenones that are hard to access otherwise. DFT studies of the reaction mechanism imply the migration insertion as the turnover-limiting step and suggest beneficial π-π interactions in the transition states.

| S-EPMC8405584 | biostudies-literature

Rhodium(III)-Catalyzed Intramolecular Annulations of Acrylic and Benzoic Acids to Alkynes.

Project description:Rh(III) catalysts can promote a formal (4 + 2) intramolecular oxidative annulation between acrylic or benzoic acid derivatives and alkynes. The reaction, which involves a C-H activation process, allows for a rapid assembly of appealing bicyclic pyran-2-ones and tricyclic isocoumarin derivatives in moderate to good yields. The α-pyrone moiety of the products provides for further manipulations to obtain relatively complex cyclic skeletons in a very simple manner.

| S-EPMC6492232 | biostudies-literature

Synthesis of Azolo[1,3,5]triazines via Rhodium(III)-Catalyzed Annulation of N-Azolo Imines and Dioxazolones.

Project description:A wide range of azolo[1,3,5]triazines were obtained by Rh(III)-catalyzed annulation of N-azolo imines and dioxazolones. The reaction proceeds by the first catalytic C-H amidation of an imidoyl C-H bond followed by cyclodehydration. Good yields were obtained for N-azolo imines derived from aminoazoles and aromatic and heteroaromatic aldehydes. A range of dioxazolone amidating reagents were employed to introduce aryl, heteroaryl, and alkyl substituents. The reaction was also performed with a benchtop setup at 1 mmol scale using microwave heating.

| S-EPMC6097942 | biostudies-literature

Rhodium-Catalyzed Enantioselective Hydroamination of Alkynes with Indolines.

Project description:The hydroamination of internal alkynes via tandem rhodium catalysis gives branched N-allylic indolines with high regio- and enantioselectivity. An acid switch provides access to the linear isomer in preference to the branched isomer by an isomerization mechanism. Mechanistic studies suggest formation of an allene intermediate, which undergoes hydroamination to generate allylic amines instead of the enamine or imine products typically observed in alkyne hydroaminations.

| S-EPMC4870006 | biostudies-literature

Rhodium(III)-Catalyzed [4+2] Annulation via C-H Activation: Synthesis of Multi-Substituted Naphthalenone Sulfoxonium Ylides.

Project description:A convenient Rh(III)-catalyzed C-H activation and cascade [4+2] annulation for the synthesis of naphthalenone sulfoxonium ylides has been developed. This method features perfect regioselectivity, mild and redox-neutral reaction conditions, and broad substrate tolerance with good to excellent yields. Preliminary mechanistic experiments were conducted and a plausible reaction mechanism was proposed. The new type naphthalenone sulfoxonium ylides could be further transformed into multi-substituted naphthols, which demonstrates the practical utility of this methodology.

| S-EPMC6572249 | biostudies-literature

Rhodium-Catalyzed [2 + 2 + 2] Cyclotrimerizations of Yndiamides with Alkynes.

Project description:Yndiamides offer opportunities for the synthesis of vicinally nitrogen-disubstituted aromatics and azacycles. Here we report the Rh-catalyzed cyclotrimerization of alkynyl yndiamides with alkynes, the regiochemical outcome of which is controlled by the electronic properties of the alkyne partner, enabling the formation of 7-aminoindolines with excellent selectivity (up to >20:1 r.r.). We also report a complementary synthesis of bicyclic 1,2-dianiline derivatives by cyclotrimerization of yndiamides with terminal diynes, where slow addition of the diyne overcomes self-dimerization.

| S-EPMC9594354 | biostudies-literature

Combining the Ugi-azide multicomponent reaction and rhodium(III)-catalyzed annulation for the synthesis of tetrazole-isoquinolone/pyridone hybrids.

Project description:An efficient sequence based on the Ugi-azide reaction and rhodium(III)-catalyzed intermolecular annulation has been established for the preparation of tetrazole-isoquinolone/pyridone hybrids. Several N-acylaminomethyltetrazoles were reacted with arylacetylenes to form the hybrid products in moderate to very good yields. The method relies on the capacity of the rhodium catalyst to promote C(sp2)-H activation in the presence of a suitable directing group. The Ugi-azide reaction provides broad molecular diversity and enables the introduction of the tetrazole moiety, which may further assist the catalytic reaction by coordinating the metal center. The scope of the isoquinolones is very wide and may be extended to the preparation of complex compounds having heterocyclic moieties such as pyridone, furan, thiophene and pyrrole, as well as the corresponding benzo-fused derivatives. The developed procedure is simple, reproducible and does not require inert conditions.

| S-EPMC6808192 | biostudies-literature

Rhodium-Catalyzed Oxidative Annulation of 2- or 7-Arylindoles with Alkenes/Alkynes Using Molecular Oxygen as the Sole Oxidant Enabled by Quaternary Ammonium Salt.

Project description:Developing an efficient catalytic system using molecular oxygen as the oxidant for rhodium-catalyzed cross-dehydrogenative coupling remains highly desirable. Herein, rhodium-catalyzed oxidative annulation of 2- or 7-phenyl-1H-indoles with alkenes or alkynes to assemble valuable 6H-isoindolo[2,1-a]indoles, pyrrolo[3,2,1-de]phenanthridines, or indolo[2,1-a]isoquinolines using the atmospheric pressure of air as the sole oxidant enabled by quaternary ammonium salt has been accomplished. Mechanistic studies provided evidence for the fast intramolecular aza-Michael reaction and aerobic reoxidation of Rh(I)/Rh(III), facilitated by the addition of quaternary ammonium salt.

| S-EPMC8433977 | biostudies-literature

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