Showing papers by "Victor Snieckus published in 2018"
TL;DR: In this article, a directed ortho-lithiation reaction of N,N-dialkyl O-aryl carbamates with sec-butyllithium/TMEDA followed by quenching with various electrophiles is described.
26 citations
TL;DR: In this article, the competitive metalation of four directed metalation group (DMG)-bearing derivatives (Cl, OMe, OMOM, and CONEt2) in comparison with the OCONEt 2 DMG is described.
17 citations
TL;DR: A new ruthenium-catalyzed hydrodemethoxylation of ortho-methoxy-benzamides and -naphthamides involving amide-directed C-OMe bond activation and hydride reduction is disclosed.
10 citations
TL;DR: The Pd-catalyzed regioselective C-H activation/arylation, /iodination, and/acetoxylation reactions of 4-arylpyrimidines using aryl iodides, N-iodosuccinimide, and (diacetoxyiodo)benzene respectively as coupling partners are described and Suzuki-Miyaura coupling and Sonogashira reactions of the resulting aryL iodides are demonstrated.
10 citations
TL;DR: Mechanical insight into the remote lateral metalation step, demonstrating the requirement of Z-cinnamamide, is described and application of this methodology to the synthesis of highly substituted 3,3'-diaryl BINOL ligands is also reported.
Abstract: A general synthesis of highly substituted 2-naphthols based on a new carbanionic reaction sequence is demonstrated. The reaction exploits the dual nature of lithium bases consisting of consecutive ring opening of readily available coumarins with either LiNEt2 or LiNiPr2 into Z-cinnamamides, thus generating a directing group in situ and allowing, by conformational freedom, a lateral directed remote metalation for ring closure to give the aryl 2-naphthols in good to excellent yields. These transformations can be combined to provide a more efficient one-pot process. Mechanistic insight into the remote lateral metalation step, demonstrating the requirement of Z-cinnamamide, is described. Application of this methodology to the synthesis of highly substituted 3,3'-diaryl BINOL ligands is also reported.
8 citations
TL;DR: In this article, a general method for the regioselective synthesis of a series of ortho-substituted chrysenyl N,N-diethyl-O-carbamates by the directed orthometalation (DoM) strategy is reported.
Abstract: A general method for the regioselective synthesis of a series of ortho-substituted chrysenyl N,N-diethyl-O-carbamates by the directed ortho-metalation (DoM) strategy is reported. The starting O-carbamates were prepared from the corresponding chrysenols, available by oxidative photochemical cyclization or directed remote metalation tactics. Chrysen-1-yl and chrysene-3-yl ring site selectivity of directed ortho-metalation (DoM) and anionic ortho-Fries rearrangement (AoF) protocols, with s-BuLi/TMEDA, followed by electrophilic quench using a selection of electrophiles, were observed, leading to new chrysenyl derivatives. 5-Chrysenyl N,N-diethyl-O-carbamate underwent instant AoF rearrangement even at −100 °C to furnish chrysenyl o-hydroxycarboxamide. Iterative DoM reactions were carried out to gain insight into the regioselectivity factors.
8 citations
TL;DR: In this paper, a systematic study of the widely used, titled name reaction transition-metal-catalyzed cross-coupling reactions with attention to context with the directed ortho metalation (DoM) is reported.
Abstract: A systematic study of the widely used, titled name reaction transition-metal-catalyzed cross-coupling reactions with attention to context with the directed ortho metalation (DoM) is reported. In general, the Suzuki–Miyaura and Negishi protocols show greater scope and better yields than the Corriu–Kumada variant, although the latter qualitatively proceeds at fastest rate but has low functional group tolerance. The Negishi process is shown to be useful for substrates with nucleophile and base-sensitive functionality and it is comparable to the Suzuki–Miyaura reaction in efficiency. The link of these cross-coupling reactions to the DoM strategy lends itself to the regioselective construction of diversely substituted aromatics and heteroaromatics.
5 citations
TL;DR: Transient-state kinetic analysis of DCHM-HOPDA turnover revealed the formation of an intermediate possessing a bathochromically shifted spectrum, similar to that of the ESred intermediate observed during tautomerization in serine-dependent hydrolases.
Abstract: LigY catalyzes the hydrolysis of a meta-cleavage product (MCP), 4,11-dicarboxy-8-hydroxy-9-methoxy-2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate (DCHM-HOPDA), in the bacterial catabolism of lignin-derived biphenyl. Most characterized MCP hydrolases are serine-dependent, with hydrolysis proceeding via enol–keto tautomerization followed by an acyl-enzyme intermediate. In contrast, LigY is Zn2+-dependent, with hydrolysis proposed to proceed via tautomerization followed by formation of a gem-diol intermediate. Transient-state kinetic analysis of DCHM-HOPDA turnover revealed the formation of an intermediate possessing a bathochromically shifted spectrum (λmax = 508 nm), similar to that of the ESred intermediate observed during tautomerization in serine-dependent hydrolases. Neither the formation (1/τ1 ≈ 137 s–1) nor the decay (1/τ2 ≈ 23 s–1) of ESred was rate-limiting (kcat = 9.7 ± 0.3 s–1). Furthermore, the rate of ESred decay was 3.4-fold slower in deuterated buffer, suggesting a proton-transfer reaction consist...
4 citations
3 citations
TL;DR: A series of alkylated 2,3‐dihydroxybiphenyls has been prepared on the gram scale by using an effective Directed ortho Metalation–Suzuki–Miyaura cross‐coupling strategy to investigate the substrate specificity of the meta‐cleavage dioxygenase BphC, a key enzyme in the microbial catabolism of biphenyl.
Abstract: A series of alkylated 2,3-dihydroxybiphenyls has been prepared on the gram scale by using an effective Directed ortho Metalation-Suzuki-Miyaura cross-coupling strategy. These compounds have been used to investigate the substrate specificity of the meta-cleavage dioxygenase BphC, a key enzyme in the microbial catabolism of biphenyl. Isolation and characterization of the meta-cleavage products will allow further study of related processes, including the catabolism of lignin-derived biphenyls.
3 citations
TL;DR: A comparative evaluation of the combined DoM-Suzuki-Miyaura and DoM−Negishi cross-coupling reactions with aryl triflates for the synthesis of substituted biaryls is described in this article.
Abstract: A comparative evaluation of the combined directed ortho metalation (DoM)–Suzuki–Miyaura and DoM–Negishi cross-coupling reactions with aryl triflates for the synthesis of substituted biaryls is described. Both ortho-zinc and ortho-boron aryl directed metalation group (DMG = CON(i-Pr)2, OCONEt2, OMOM, NHBoc) substrates were evaluated. The superiority of the DoM–Negishi over the DoM–Suzuki–Miyaura reaction in operational convenience and mild reaction conditions is noted. Orthogonal Negishi and Suzuki–Miyaura with Corriu–Kumada reactions for the synthesis of a teraryl derivative is also reported.
20 Jul 2018
TL;DR: In this article, a general synthesis of highly substituted 2-naphthols based on a new carbanionic reaction sequence is demonstrated, where the reaction exploits the dual nature of lithium bases consisting of consecutive ring opening of readily available coumarins with LiNEt2 or LDA to Z-cinnamides generating a directing group in situ and allowing, by conformational freedom, a lateral directed remote metalation ‐ ring closure reaction to give the aryl 2naphthsols in good to excellent yields.
Abstract: A general synthesis of highly substituted 2‐naphthols based on a new carbanionic reaction sequence is demonstrated. The reaction exploits the dual nature of lithium bases consisting of consecutive ring opening of readily available coumarins with LiNEt2 or LDA to Z‐cinnamamides generating a directing group in situ and allowing, by conformational freedom, a lateral directed remote metalation ‐ ring closure reaction to give the aryl 2‐naphthols in good to excellent yields. These transformations can be combined to provide a more efficient one pot process. Mechanistic insight into the remote lateral metalation step demonstrating the requirement of Z‐cinnamamide is described. Application of this methodology to the synthesis of highly substituted 3,3'‐diaryl BINOL ligands is also reported.
TL;DR: The use of two biphenyl sulfonic acid ligands for the catalytic C-N cross coupling of aryl halides with anilines, 3-aminopyridine, and secondary amines is reported, representing a significant improvement compared to state of the art methods especially with regards to the removal of palladium.