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Search for "singlet carbene" in Full Text gives 5 result(s) in Beilstein Journal of Organic Chemistry.
One hundred years of benzotropone chemistry
- Arif Dastan,
- Haydar Kilic and
- Nurullah Saracoglu
Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98
Graphical Abstract
Scheme 1: Tropone (1), tropolone (2) and their resonance structures.
Figure 1: Natural products containing a tropone nucleus.
Figure 2: Possible isomers 11–13 of benzotropone.
Scheme 2: Synthesis of benzotropones 11 and 12.
Scheme 3: Oxidation products of benzotropylium fluoroborate (16).
Scheme 4: Oxidation of 7-bromo-5H-benzo[7]annulene (22).
Scheme 5: Synthesis of 4,5-benzotropone (11) using o-phthalaldehyde (27).
Scheme 6: Synthesis of 4,5-benzotropone (11) starting from oxobenzonorbornadiene 31.
Scheme 7: Acid-catalyzed cleavage of oxo-bridge of 34.
Scheme 8: Synthesis of 4,5-benzotropone (11) from o-xylylene dibromide (38).
Scheme 9: Synthesis of 4,5-benzotropone (11) via the carbene adduct 41.
Scheme 10: Heck coupling strategy for the synthesis of 11.
Scheme 11: Synthesis of benzofulvalenes via carbonyl group of 4,5-benzotropone (11).
Figure 3: Some cycloheptatrienylium cations.
Scheme 12: Synthesis of condensation product 63 and its subsequent oxidative cyclization products.
Figure 4: A novel series of benzo[7]annulenes prepared from 4,5-benzotropone (11).
Scheme 13: Preparation of substituted benzo[7]annulene 72 using the Mukaiyama-Michael reaction.
Figure 5: Possible benzo[7]annulenylidenes 73–75.
Scheme 14: Thermal and photochemical decomposition of 7-diazo-7H-benzo[7]annulene (76) and the trapping of int...
Scheme 15: Synthesis of benzoheptafulvalene 86.
Scheme 16: Synthesis of 7-(diphenylmethylene)-7H-benzo[7]annulene (89).
Scheme 17: Reaction of 4,5-benzotropone (11) with dimethyl diazomethane.
Scheme 18: Synthesis of dihydrobenzomethoxyazocine 103.
Scheme 19: Synthesis and reducibility of benzo-homo-2-methoxyazocines.
Scheme 20: Synthesis of 4,5-benzohomotropones 104 and 115 from 4,5-benzotropones 11 and 113.
Scheme 21: A catalytic deuterogenation of 4,5-benzotropone (11) and synthesis of 5-monosubstituted benzo[7]ann...
Scheme 22: Synthesis of methyl benzo[7]annulenes 131 and 132.
Scheme 23: Ambident reactivity of halobenzo[7]annulenylium cations 133a/b.
Scheme 24: Preparation of benzo[7]annulenylidene–iron complexes 147.
Scheme 25: Synthesis of 1-ethynylbenzotropone (150) and the etheric compound 152 from 4,5-benzotropone (11) wi...
Scheme 26: Thermal decomposition of 4,5-benzotropone (11).
Scheme 27: Reaction of 4,5-benzotropone (11) with 1,2-ethanediol and 1,2-ethanedithiol.
Scheme 28: Conversions of 1-benzosuberone (162) to 2,3-benzotropone (12).
Scheme 29: Synthesis strategies for 2,3-bezotropone (12) using 1-benzosuberones.
Scheme 30: Oxidation-based synthesis of 2,3-benzotropone (12) via 1-benzosuberone (162).
Scheme 31: Synthesis of 2,3-benzotropone (12) from α-tetralone (171) via ring-expansion.
Scheme 32: Preparation of 2,3-benzotropone (12) by using of benzotropolone 174.
Figure 6: Benzoheptafulvenes as condensation products of 2,3-benzotropone (12).
Scheme 33: Conversion of 2,3-benzotropone (12) to tosylhydrazone salt 182 and gem-dichloride 187.
Figure 7: Benzohomoazocines 191–193 and benzoazocines 194–197.
Scheme 34: From 2,3-benzotropone (12) to carbonium ions 198–201.
Scheme 35: Cycloaddition reactions of 2,3-benzotropone (12).
Scheme 36: Reaction of 2,3-benzotropone (12) with various reagents and compounds.
Figure 8: 3,4-Benzotropone (13) and its resonance structure.
Scheme 37: Synthesis of 6,7-benzobicyclo[3.2.0]hepta-3,6-dien-2-one (230).
Figure 9: Photolysis and thermolysis products of 230.
Figure 10: Benzotropolones and their tautomeric structures.
Scheme 38: Synthesis strategies of 4,5-benzotropolone (238).
Scheme 39: Synthesis protocol for 2-hydroxy-4,5-benzotropone (238) using oxazole-benzo[7]annulene 247.
Figure 11: Some quinoxaline and pyrazine derivatives 254–256 prepared from 4,5-benzotropolone (238).
Scheme 40: Nitration product of 4,5-benzotropolone (238) and its isomerization to 1-nitro-naphthoic acid (259)....
Scheme 41: Synthesis protocol for 6-hydroxy-2,3-benzotropone (239) from benzosuberone (162).
Scheme 42: Various reactions via 6-hydroxy-2,3-benzotropone (239).
Scheme 43: Photoreaction of 6-hydroxy-2,3-benzotropone (239).
Scheme 44: Synthesis of 7-hydroxy-2,3-benzotropone (241) from benzosuberone (162).
Scheme 45: Synthesis strategy for 7-hydroxy-2,3-benzotropone (241) from ketone 276.
Scheme 46: Synthesis of 7-hydroxy-2,3-benzotropone (241) from β-naphthoquinone (280).
Scheme 47: Synthesis of 7-hydroxy-2,3-benzotropone (241) from bicyclic endoperoxide 213.
Scheme 48: Synthesis of 7-hydroxy-2,3-benzotropone (241) by ring-closing metathesis.
Figure 12: Various monosubstitution products 289–291 of 7-hydroxy-2,3-benzotropone (241).
Scheme 49: Reaction of 7-hydroxy-2,3-benzotropone (241) with various reagents.
Scheme 50: Synthesis of 4-hydroxy-2,3-benzotropones 174 and 304 from diketones 300/301.
Scheme 51: Catalytic hydrogenation of diketones 300 and 174.
Scheme 52: Synthesis of halo-benzotropones from alkoxy-naphthalenes 306, 307 and 310.
Figure 13: Unexpected byproducts 313–315 during synthesis of chlorobenzotropone 309.
Figure 14: Some halobenzotropones and their cycloadducts.
Scheme 53: Multisep synthesis of 2-chlorobenzotropone 309.
Scheme 54: A multistep synthesis of 2-bromo-benzotropone 26.
Scheme 55: A multistep synthesis of bromo-2,3-benzotropones 311 and 316.
Scheme 56: Oxidation reactions of 8-bromo-5H-benzo[7]annulene (329) with some oxidants.
Scheme 57: Synthesis of 2-bromo-4,5-benzotropone (26).
Scheme 58: Synthesis of 6-chloro-2,3-benzotropone (335) using LiCl and proposed intermediate 336.
Scheme 59: Reaction of 7-bromo-2,3-benzotropone (316) with methylamine.
Scheme 60: Reactions of bromo-2,3-benzotropones 26 and 311 with dimethylamine.
Scheme 61: Reactions of bromobenzotropones 311 and 26 with NaOMe.
Scheme 62: Reactions of bromobenzotropones 26 and 312 with t-BuOK in the presence of DPIBF.
Scheme 63: Cobalt-catalyzed reductive cross-couplings of 7-bromo-2,3-benzotropone (316) with cyclic α-bromo en...
Figure 15: Cycloadduct 357 and its di-π-methane rearrangement product 358.
Scheme 64: Catalytic hydrogenation of 2-chloro-4,5-benzotropone (311).
Scheme 65: Synthesis of dibromo-benzotropones from benzotropones.
Scheme 66: Bromination/dehydrobromination of benzosuberone (162).
Scheme 67: Some transformations of isomeric dibromo-benzotropones 261A/B.
Scheme 68: Transformations of benzotropolone 239B to halobenzotropolones 369–371.
Figure 16: Bromobenzotropolones 372–376 and 290 prepared via bromination/dehydrobromination strategy.
Scheme 69: Synthesis of some halobenzotropolones 289, 377 and 378.
Figure 17: Bromo-chloro-derivatives 379–381 prepared via chlorination.
Scheme 70: Synthesis of 7-iodo-3,4-benzotropolone (382).
Scheme 71: Hydrogenation of bromobenzotropolones 369 and 370.
Scheme 72: Debromination reactions of mono- and dibromides 290 and 375.
Figure 18: Nitratation and oxidation products of some halobenzotropolenes.
Scheme 73: Azo-coupling reactions of some halobenzotropolones 294, 375 and 378.
Figure 19: Four possible isomers of dibenzotropones 396–399.
Figure 20: Resonance structures of tribenzotropone (400).
Scheme 74: Two synthetic pathways for tribenzotropone (400).
Scheme 75: Synthesis of tribenzotropone (400) from dibenzotropone 399.
Scheme 76: Synthesis of tribenzotropone (400) from 9,10-phenanthraquinone (406).
Scheme 77: Synthesis of tribenzotropone (400) from trifluoromethyl-substituted arene 411.
Figure 21: Dibenzosuberone (414).
Figure 22: Reduction products 415 and 416 of tribenzotropone (400).
Figure 23: Structures of tribenzotropone dimethyl ketal 417 and 4-phenylfluorenone (412) and proposed intermed...
Figure 24: Structures of benzylidene- and methylene-9H-tribenzo[a,c,e][7]annulenes 419 and 420 and chiral phos...
Figure 25: Structures of tetracyclic alcohol 422, p-quinone methide 423 and cation 424.
Figure 26: Structures of host molecules 425–427.
Scheme 78: Synthesis of non-helical overcrowded derivatives syn/anti-431.
Figure 27: Hexabenzooctalene 432.
Figure 28: Structures of possible eight isomers 433–440 of naphthotropone.
Scheme 79: Synthesis of naphthotropone 437 starting from 1-phenylcycloheptene (441).
Scheme 80: Synthesis of 10-hydroxy-11H-cyclohepta[a]naphthalen-11-one (448) from diester 445.
Scheme 81: Synthesis of naphthotropone 433.
Scheme 82: Synthesis of naphthotropones 433 and 434 via cycloaddition reaction.
Scheme 83: Synthesis of naphthotropone 434 starting from 452.
Figure 29: Structures of tricarbonyl(tropone)irons 458, and possible cycloadducts 459.
Scheme 84: Synthesis of naphthotropone 436.
Scheme 85: Synthesis of precursor 465 for naphthotropone 435.
Scheme 86: Generation of naphthotropone 435 from 465.
Figure 30: Structures of tropylium cations 469 and 470.
Figure 31: Structures of tropylium ions 471+.BF4−, 472+.BF4−, and 473+.BF4−.
Scheme 87: Synthesis of tropylium ions 471+.BF4− and 479+.ClO4−.
Scheme 88: Synthesis of 1- and 2-methylanthracene (481 and 482) via carbene–carbene rearrangement.
Figure 32: Trapping products 488–490.
Scheme 89: Generation and chemistry of a naphthoannelated cycloheptatrienylidene-cycloheptatetraene intermedia...
Scheme 90: Proposed intermediates and reaction pathways for adduct 498.
Scheme 91: Exited-state intramolecular proton transfer of 505.
Figure 33: Benzoditropones 506 and 507.
Scheme 92: Synthesis of benzoditropone 506e.
Scheme 93: Synthetic approaches for dibenzotropone 507 via tropone (1).
Scheme 94: Formation mechanisms of benzoditropone 507 and 516 via 515.
Scheme 95: Synthesis of benzoditropones 525 and 526 from pyromellitic dianhydride (527).
Figure 34: Possible three benzocyclobutatropones 534–536.
Scheme 96: Synthesis of benzocyclobutatropones 534 and 539.
Scheme 97: Synthesis attempts for benzocyclobutatropone 545.
Scheme 98: Generation and trapping of symmetric benzocyclobutatropone 536.
Scheme 99: Synthesis of chloro-benzocyclobutatropone 552 and proposed mechanism of fluorenone derivatives.
Scheme 100: Synthesis of tropolone analogue 559.
Scheme 101: Synthesis of tropolones 561 and 562.
Figure 35: o/p-Tropoquinone rings (563 and 564) and benzotropoquinones (565–567).
Scheme 102: Synthesis of benzotropoquinone 566.
Scheme 103: Synthesis of benzotropoquinone 567 via a Diels–Alder reaction.
Figure 36: Products 575–577 through 1,2,3-benzotropoquinone hydrate 569.
Scheme 104: Structures 578–582 prepared from tropoquinone 567.
Figure 37: Two possible structures 583 and 584 for dibenzotropoquinone, and precursor compound 585 for 583.
Scheme 105: Synthesis of saddle-shaped ketone 592 using dibenzotropoquinone 584.
On the cause of low thermal stability of ethyl halodiazoacetates
- Magnus Mortén,
- Martin Hennum and
- Tore Bonge-Hansen
Beilstein J. Org. Chem. 2016, 12, 1590–1597, doi:10.3762/bjoc.12.155
- nucleophilicity can be inferred from the NBO charges. Based only on NBO charges, halodiazoacetates may be expected to be even less nucleophilic than diethyl diazomalonate (see Supporting Information File 2 for the numbers). All of the investigated diazo compounds thermally extrude N2 to initially form a singlet
- carbene with an empty p-orbital at the carbene carbon (see Supporting Information File 2 for bond angles and bond lengths). The NBO atomic charges for the singlet carbenes from 1 and 2a,b, and d are shown in Figure 6. The calculations predict the following order of electrophilicity for the carbenes
Graphical Abstract
Figure 1: Relative stability and nucleophilicity of non-stabilized (R = H, alkyl) diazo compounds (left) and ...
Scheme 1: Synthesis of ethyl halodiazoacetates [11].
Figure 2: a) The decay of 2b in toluene-d8 at 35 °C. b) The plot of log(Δ[2b]) vs time.
Scheme 2: Proposed rate determining step for the thermal decomposition of 2a–c.
Figure 3: Transition-state energies (kcal/mol) for the release of N2 and formation of the singlet carbenes. T...
Figure 4: Thermal stability of 1 and 2a–c, and the α-substituents’ contribution to π-donation.
Figure 5: NBO atomic charges and IR stretching frequencies calculated [21] and experimentally recorded for 1 and ...
Figure 6: NBO atomic charges of the singlet carbenes from 1 and 2a,b, and d.
Figure 7: Relative thermal stability of halodiazoacetates (red color).
Figure 8: Relative nucleophilicity of halodiazoacetates (red color).
Enantioselective carbenoid insertion into C(sp3)–H bonds
- J. V. Santiago and
- A. H. L. Machado
Beilstein J. Org. Chem. 2016, 12, 882–902, doi:10.3762/bjoc.12.87
- in this transformation, more efforts should be focused towards the development of new and robust heterogeneous catalytic systems. This strategy can reduce the costs related to metals like rhodium or iridium and can also contribute to reduce the disposal of these metals in the environment. Singlet
- carbene, triplet carbene and carbenoids. Classification of the carbenoid intermediates by the electronic nature of the groups attached to the divalent carbene carbon. Chiral bis(oxazoline) ligands used in enantioselective copper carbenoid insertion. Chemical structures of complexes (R)-18 and (S)-18
Graphical Abstract
Figure 1: Singlet carbene, triplet carbene and carbenoids.
Figure 2: Classification of the carbenoid intermediates by the electronic nature of the groups attached to th...
Figure 3: Chiral bis(oxazoline) ligands used in enantioselective copper carbenoid insertion.
Scheme 1: Pioneering work of Peter Yates on the carbenoid insertion reaction into X–H bonds (where X = O, S, ...
Scheme 2: Copper carbenoid insertion into C(sp3)–H bond of a stereogenic center with full retention of the as...
Scheme 3: Carbenoid insertion into a C(sp3)–H bond as the key step of the Taber’s (+)-α-cuparenone (8) synthe...
Scheme 4: First enantioselective carbenoid insertion into C–O bonds catalyzed by chiral metallic complexes.
Figure 4: Chemical structures of complexes (R)-18 and (S)-18.
Scheme 5: Asymmetric carbenoid insertions into C(sp3)–H bonds of cycloalkanes catalyzed by chiral rhodium car...
Scheme 6: First diastereo and enantioselective intermolecular carbenoid insertion into tetrahydrofuran C(sp3)...
Scheme 7: Simplified mechanism of the carbenoid insertion into a C(sp3)–H bond.
Scheme 8: Nakamura’s carbenoid insertion into a C(sp3)–H bond catalytic cycle.
Scheme 9: Investigation of the relationship between the electronic characteristics of the substituent X attac...
Scheme 10: Empirical model to predict the stereoselectivity of the donor/acceptor dirhodium carbenoid insertio...
Scheme 11: Asymmetric insertion of copper carbenoids in C(sp3)–H bonds to prepare trans-γ-lactam.
Figure 5: Iridium catalysts used by Suematsu and Katsuki for carbenoid insertion into C(sp3)–H bonds.
Scheme 12: Chiral porphyrin iridium complex catalyzes the carbenoid insertion into bis-allylic C(sp3)–H bonds.
Scheme 13: Chiral porphyrin iridium complex catalyzes the carbenoid insertion into tetrahydrofuran C(sp3)–H bo...
Scheme 14: Chiral porphyrin–iridium complex catalyzes the intramolecular carbenoid insertion into C(sp3)–H bon...
Scheme 15: Chiral bis(oxazoline)–iridium complex catalyzes the carbenoid insertion into bis-allylic C(sp3)–H b...
Scheme 16: New cyclopropylcarboxylate-based chiral catalyst to enantioselective carbenoid insertion into the e...
Scheme 17: Regio- and enantioselective carbenoid insertion into the C(sp3)–H bond catalyzed by a new bulky cyc...
Scheme 18: Regio and diastereoselective carbenoid insertion into the C(sp3)–H bond catalyzed by a new bulky cy...
Scheme 19: 2,2,2-Trichloroethyl (TCE) aryldiazoacetates to improve the scope, regio- and enantioselective of t...
Scheme 20: Sequential C–H functionalization approach to 2,3-dihydrobenzofurans.
Scheme 21: Enantioselective intramolecular rhodium carbenoid insertion into C(sp3)–H bonds to afford cis-disub...
Scheme 22: Enantioselective intramolecular rhodium carbenoid insertion into C(sp3)–H bonds to afford cis-2-vin...
Scheme 23: First rhodium porphyrin-based catalyst for enantioselective carbenoid insertion into C(sp3)–H bond.
Scheme 24: Rhodium porphyrin-based catalyst for enantioselective carbenoid insertion into benzylic C(sp3)–H bo...
Dimerisation, rhodium complex formation and rearrangements of N-heterocyclic carbenes of indazoles
- Zong Guan,
- Jan C. Namyslo,
- Martin H. H. Drafz,
- Martin Nieger and
- Andreas Schmidt
Beilstein J. Org. Chem. 2014, 10, 832–840, doi:10.3762/bjoc.10.79
- standard conditions (25 °C, 1 atm) was found to be 3.4 kcal/mol [20]. Alternatively, indazolium salts 2 can be deprotonated by various bases to give indazol-3-ylidenes 3 [22]. The chemistry of indazol-3-ylidene, which is a singlet carbene, is due to the considerable donor strength of the carbene atom which
Graphical Abstract
Scheme 1: Generation of indazol-3-ylidenes.
Scheme 2: Reaction products of indazol-3-ylidenes in heterocycle synthesis.
Scheme 3: Syntheses of acridines from indazol-3-ylidenes.
Scheme 4: Dimerisation of indazol-3-ylidenes to spiro compounds.
Figure 1: Diagnostic 1H and 13C NMR chemical shifts of the Z and E configuration isomer in CDCl3.
Figure 2: Molecular structure of 14c, displacement parameters are drawn at 50% probability level.
Scheme 5: Rhodium complex formation.
Figure 3: Structure of the cation of 15e, displacement parameters are drawn at 50% probability level.
Scheme 6: Rearrangement of the spiro compounds on heating.
Figure 4: Molecular structure of 16b, displacement parameters are drawn at 50% probability level.
Intramolecular hydroxycarbene C–H-insertion: The curious case of (o-methoxyphenyl)hydroxycarbene
- Dennis Gerbig,
- David Ley,
- Hans Peter Reisenauer and
- Peter R. Schreiner
Beilstein J. Org. Chem. 2010, 6, 1061–1069, doi:10.3762/bjoc.6.121
- intermediate leading to the tautomeric formyl group. Thermochemical computations at M06-2X/cc-pVDZ in conjunction with a self-consistent solvent reaction field model support this suggested reaction pathway. Keywords: benzofuran; C–H-insertion; hydroxycarbene; singlet carbene; tunneling; Introduction
Graphical Abstract
Scheme 1: Unimolecular reactivity of hydroxycarbenes under cryogenic conditions: [1,2]H-Tunneling of 1 and 3 (...
Scheme 2: A selection of heterocarbenes that undergo intramolecular C–H insertions.
Scheme 3: Attempted generation of 5 and d-5 as well as their corresponding insertion products.
Scheme 4: Proposed mechanism for the generation of 8 and 9. The [1,2]H-tunneling process apparently cannot co...
Figure 1: Unmodified matrix IR spectrum (Ar, 11 K) of the pyrolysis (600 °C) of 5. Traces of 9 are indicated ...
Figure 2: Unmodified matrix IR spectrum (Ar, 11 K) of the pyrolysis (600 °C) of d-5. Traces of 9 are indicate...
Scheme 5: Decay of the 2,3-dihydrobenzofuran-3-ol molecular radical cation (8+•).
Scheme 6: Attempted generation of 12 and the actual pyrolysis product 11.
Scheme 7: Unanticipated reaction of 6 upon heating in xylenes.
Scheme 8: Potential energy hypersurface of (o-methoxyphenyl)hydroxycarbene (5) (not drawn to scale; ZPVE incl...
Scheme 9: Acid-catalyzed generation of 7 by unreacted 6.
