Copper-Catalyzed Ring-Opening/Borylation of Cyclopropenes

CCS Chemistry, Год журнала: 2021, Номер 4(4), С. 1232 - 1237

Опубликована: Май 21, 2021

Open AccessCCS ChemistryCOMMUNICATION1 Apr 2022Copper-Catalyzed Ring-Opening/Borylation of Cyclopropenes Ming-Yao Huang†, Yu-Tao Zhao†, Hao Chai, Cheng-Da Zhang and Shou-Fei Zhu Huang† The State Key Laboratory Institute Elemento-Organic Chemistry, College Nankai University, Tianjin 300071 , Zhao† Chai *Corresponding author: E-mail Address: [email protected] https://doi.org/10.31635/ccschem.021.202100921 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Since organoboron compounds readily undergo a diverse array transformations are widely used in various fields, the development C–B-bond-forming reactions have attracted considerable attention. Herein, we report new method for forming C–B bonds by means Cu-catalyzed ring-opening/borylation cyclopropenes. This provides efficient access type stable allylborane–Lewis base adduct, which is versatile synthon. configuration products can be well controlled with this method, some configurations obtained inaccessible other catalytic methods generating allylborons. Mechanistic studies indicated that proceed via insertion an alkenyl Cu carbene—generated situ cyclopropene ring opening—into B–H bond; ring-opening step determines both rate stereochemistry. Download figure PowerPoint Introduction Organoboron broad applications organic synthesis,1,2 medicinal chemistry,3,4 materials science.5,6 Therefore, form has been area longstanding interest field synthetic chemistry. transition metal-catalyzed carbenes into was first disclosed 2013, it become good construction bonds.7–10 When diazo compounds,11–17 alkynes,18,19 or sulfoxonium ylides20,21 as carbene precursors, enables many novel organoboranes high yields regioselectivity and, cases, enantioselectivity (Scheme 1a). Quite recently, unsaturated also established construct C(sp2)–B bonds.22 precursors will undoubtedly increase utility constructing known methods, can, turn, expected provide opportunities investigating bioactivity material properties organoboranes. Scheme 1 | (a) Known bond reactions. (b) Copper-catalyzed Cyclopropenes23–27 useful precursors: metal-promoted opening these well-established metal generation, related carbene-transfer synthesis.28–33 protocol copper carbenoids, were generated cyclopropenes, borane–Lewis adducts 1b). not only represents demonstration carbenoids from cyclopropenes inserted but allylborane product accessible using methodology. Results Discussion We began our study reaction 1a trimethylamine–borane adduct 2a dichloromethane (DCM) at 25 °C catalysis Cu(MeCN)4PF6 (Table 1). In absence ligand, trace amount desired detected, dimerization observed instead (entry addition bisphosphine ligand failed improve yield (entries 2 3); however, presence monophosphine JohnPhos ( L3) afforded 3aa 83% NMR spectroscopy 4). lower activity biphosphine modified complex might contribute its higher steric hindrance weaker Lewis acidity compared monophosphine-modified complex. Changing substituent on biphenyl skeleton phosphorous atom did 5–10). Solvent effects investigated L3, all tested solvents, except dichloroethane (DCE), dramatically decreased 11–15). temperature increased 40 °C, slightly increased, time required full conversion 16). Notably, sensitive bulk basicity base. Specifically, borane trimethylamine yields; bases, including secondary tertiary amines, pyridines, phosphines, N-heterocarbenes, displayed moderate poor Supporting Information Table S1). Copper-Catalyzed Reaction Cyclopropene 1a: Optimization Conditions Entrya L Solv. Conv. (%)b Yield None DCM 100 Trace L1 3 L2 4 L3 96 83 5 L4 69 6 L5 49 7 L6 8 L7 14 9 L8 81 10 L9 70 11 DCE 79 12 CHCl3 13 Toluene 88 45 THF 21 15 cHexanes 66 18 16c 85 (82) aReaction conditions: 1a/ 2a/Cu(MeCN)4PF6/ = 0.2/0.8/0.01/0.012 (mmol), mL solvent. bConversion determined 1H analysis 1,3,5-trimethoxylbenzene internal standard. main byproduct dimer 4. Value parentheses isolated 0.3 mmol scale. cReaction performed h. Using optimized conditions 1, entry 16), assessed scope transformation carrying out 3,3-dialkyl substituted 2). Symmetrical 3,3-dialkyl-substituted corresponding allylboranes 3aa– 3da). stereoselectivity asymmetrical could regulated changing owing differences between two C3 substituents. Under standard 3-methyl-3-adamantyl-substituted gave E-allylborane 3ea (65% yield). contrast, smaller bias, such 3-methyl-3-cyclohexyl cyclopropene, 3-ethyl-3-cyclohexyl 3-methyl-3-cyclopentyl showed E 3fa– 3ha) more hindered L9. A methyl benzyl substituents, similar size, E/Z mixture 3ia trimethylamine-borane. 1/2a/Cu(MeCN)4PF6/L3 0.3/1.2/0.015/0.018 DCM. Isolated given. ratio >20:1 unless otherwise noted. Ad adamantyl. aL9 16 then attempted expand 3-aryl-3-alkyl-substituted 5. found 3-methyl-3-phenyl 5a) under 38% E-allylboron 6aa, along intramolecular C–H S2, However, optimization revealed results improved L9, 71% E- 6aa 5). selectivity unique: usually afford Z-allylboron compounds.34,35 With newly hand, systematically evaluated variety 3-alkyl-3-aryl 3). para-methyl -methoxyl groups phenyl (compare 6ba 6ca 6aa), whereas para-F -Cl atoms had little influence 6da 6ea). introduction strongly electron-withdrawing para-trifluoromethyl group markedly reduced 6fa). Substrates meta substituency yields, substituents no effect 6ga 6ha). highly 3-phenyl group; ortho-phenyl 6ia. fused rings (i.e., 3-benzo[d][1,3]dioxole 3-naphthyl) 6ja 6ka) acceptable selectivities. 3-methyl group, 3-ethyl 3-cyclopropyl tolerated 6la 6ma). Fused 6na 6oa), decreasing size. Hydroxyl ester 6pa 6qa), sulfonyl phthalimido amide inhibited thus 6ra 6sa). bearing vinyl conjugated allylic boranes 6ta 6ua). Finally, 3,3-diaryl-substituted either electron-rich 4-methoxylphenyl groups, allylboron 6va 6wa; byproducts (not shown). aryl- alkenyl-substituted 5/2a/Cu(MeCN)4PF6/L9 Ms methanesulfonyl, NPht phthalimido. To illustrate potential protocol, set one products. First, carried gram-scale obtain (71% yield, > 20:1; 4a). Borane easily transformed boronates pinacol N-methyl imidodiacetic acid, respectively 4b). Heating aqueous air efficiently oxidized hydroxyl 9). Stereospecific allylboration benzaldehyde phenylpropyl aldehyde water homoallylic alcohols diastereoselectivity. Interestingly, N-chlorosuccinimide chlorinated novel, chloro-borane amine 12). Gram-scale experiment 6aa. (1) pinacol, THF, h; (2) toluene/DMSO 5:1, (3) H2O, air, 60 (4) PhCHO, (5) h, aldehyde, 4Å molecular sieves, (6) N-chlorosuccinimide, DCM, room temperature, min. tetrahydrofuran; DMSO, dimethyl sulfoxide. control experiments shed light mechanism reaction. deuterium-labeling boron deuterium added same carbon 5a). kinetic isotope negligible (1.1), indicating hydrogen-transfer fast 5b). 5a deuterated protonated H–D exchange occur 5c). Moreover, separate three different almost identical distributions intermolecular produced insertion; result demonstrated nature 5d). Control proposed mechanism. On basis experiments, propose shown 5e. undergoes Cu(I)-catalyzed Z-vinyl Cu(I) intermediate. probably rate-determining according 5b) stereochemistry intermediate (the Z- E-carbene). E-carbene subsequently captured three-membered-ring state product, while Z-carbene tends electrophilic attack formal explain ratios 6fa 6oa. electron-deficient para-trifluoromethylphenyl decreases Z-carbene, portion generate small product. case 6oa, strain inhibits favors Z-carbene. Conclusions developed mild substrate synthesize γ,γ-disubstituted adducts. These transformations, illustrating great show proceeds carbene, ring, bond. facilitate structurally synthesis organoborons. available includes general procedures cylcopropenes, evaluation base-borane adducts, additional results, characteristic data, spectra compounds. Conflict Interest There conflict report. Funding research made possible generous grant National Natural Science Foundation China (nos. 21625204 21971119), "111" project (B06005) Ministry Education China, Program Support Top-notch Young Professionals, Key-Area Research Development Guangdong Province (no. 2020B010188001) financial support. 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Язык: Английский

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Enantioselective Indole Insertion Reactions of α-Carbonyl Sulfoxonium Ylides

Organic Letters, Год журнала: 2021, Номер 23(24), С. 9446 - 9450

Опубликована: Дек. 2, 2021

The first example of organocatalytic enantioselective C–H insertion reactions indoles and sulfoxonium ylides is reported. Under the influence phosphoric acid catalysis, levels enantiocontrol in range 20–93% ee moderate yields (up to 50%) were achieved for 29 examples formal free α-carbonyl ylides. No nitrogen protection on indole necessary.

Язык: Английский

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Visible-light-driven PhSSPh-catalysed regioselective hydroborylation of α,β-unsaturated carbonyl compounds with NHC-boranes

Chemical Communications, Год журнала: 2022, Номер 58(60), С. 8380 - 8383

Опубликована: Янв. 1, 2022

A photo-induced transition-metal-free regioselective hydroborylation of α,β-unsaturated carbonyl compounds is developed. The PhSSPh reagent was employed as the photocatalyst, and NHC-BH3 used boron source. This transformation shows a broad substrate scope provides wide range α-borylcarbonyl molecules in good to excellent yields.

Язык: Английский

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One-pot synthesis of 3-trifluoromethylbenzo[b][1,4]oxazines from CF₃-imidoyl sulfoxonium ylides with 2-bromophenols

Chemical Communications, Год журнала: 2022, Номер 58(89), С. 12443 - 12446

Опубликована: Янв. 1, 2022

Herein, a method to access 3-trifluoromethyl-1,4-benzoxazines from CF3-imidoyl sulfoxonium ylides and 2-bromophenols has been demonstrated. This synthetic protocol proceeds via one-pot two-step sequence that includes the lithium-bromide-promoted O-H insertion of annulation, merits broad substrate scope, excellent functional tolerance operational simplicity, which provides an alternative means obtaining CF3-substituted heterocycles.

Язык: Английский

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Synthesis of I(III)/S(VI) reagents and their reactivity in photochemical cycloaddition reactions with unsaturated bonds

Nature Communications, Год журнала: 2022, Номер 13(1)

Опубликована: Ноя. 3, 2022

The development of novel methodologies for the introduction sulfoxonium group under mild conditions is appealing but remains underexplored. Herein we report synthesis a class hypervalent iodine reagents with transferrable group. These compounds enable mixed iodonium-sulfoxonium ylide reactivity. well-defined are examined in visible-light-promoted cyclization reactions wide range unsaturated bonds including alkenes, alkynes, nitriles, and allenes. Two distinct pathways identified, which controlled by substituent bond. cycloaddition protocol features simple operation, reaction conditions, excellent functional tolerance, affording broad sulfoxonium-containing cyclic structures moderate to yields. Furthermore, sufoxonium product can be transformed into diverse groups structural motifs via single electron transfer transition-metal catalysis.

Язык: Английский

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