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Search for "electrocyclic ring-closure" 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
- compared by both experimental techniques and by means of MNDO calculations (Scheme 26) [131]. While the key steps for the thermal decomposition of tropones are electrocyclic ring closure and cheletropic CO extrusion to give an aromatic system, the cationic reactions occur with ring closure followed by the
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.
Tandem processes promoted by a hydrogen shift in 6-arylfulvenes bearing acetalic units at ortho position: a combined experimental and computational study
- Mateo Alajarin,
- Marta Marin-Luna,
- Pilar Sanchez-Andrada and
- Angel Vidal
Beilstein J. Org. Chem. 2016, 12, 260–270, doi:10.3762/bjoc.12.28
- 10a and 11a can lead respectively to the final benzindenes 5a and 6a. Thus, intermediate 11a undergoes a disrotatory 6π-electrocyclic ring closure [49] via the transition structure TS6 to give the tricyclic species 13a. By an analogous electrocyclic ring closure through TS7, compound 10a is converted
Graphical Abstract
Scheme 1: Lewis acid-catalyzed [1,4]-H transfer/1,5-electrocyclization tandem processes of benzylidenemalonat...
Scheme 2: Preparation of benz[f]indenes 5 and 6. Reagents and conditions: i) cyclopentadiene, pyrrolidine, an...
Scheme 3: Postulated reaction path for the conversion 3a → 5a + 6a initiated by a [1,4]-hydride shift.
Scheme 4: Alternative mechanistic paths for the conversion 3a → 5a + 6a initiated by [1,5]-, [1,7]- or [1,9]-...
Scheme 5: Postulated outcome of the conversion 14 → 18 + 19 initiated by a [1,4]-deuteride shift.
Scheme 6: Preparation of deuterated benz[f]indenes 18 + 19 and 21 + 22. Reagents and conditions: i) DMSO, mic...
Scheme 7: Reagents and conditions: i) triethylamine (10%), DMSO, rt, 2 h.
Scheme 8: Preparation of benz[f]indenes 25 and 26. Reagents and conditions: i) cyclopentadiene, pyrrolidine, ...
Scheme 9: Mechanistic paths for the conversion of fulvene 3a into the benz[f]indenes 5a and 6a showing the en...
Figure 1: Optimized geometry of transition structures TS1-A, TS1-B, and TS1-C computed at the B3LYP/6-31+G** ...
Simple two-step synthesis of 2,4-disubstituted pyrroles and 3,5-disubstituted pyrrole-2-carbonitriles from enones
- Murat Kucukdisli,
- Dorota Ferenc,
- Marcel Heinz,
- Christine Wiebe and
- Till Opatz
Beilstein J. Org. Chem. 2014, 10, 466–470, doi:10.3762/bjoc.10.44
- )nitriles can be used as versatile and readily accessible pronucleophiles, e.g. for the construction of γ-amino acids [32], pyrrolidines [33], as well as pyrroles [34][35]. If an additional conjugated double bond is present, the anions of α-(alkylideneamino)nitriles 3 can undergo an electrocyclic ring
- closure to furnish 3,4-dihydro-2H-pyrrole-2-carbonitriles 6 after reprotonation [36]. If the products are devoid of an additional substituent in 2-position, the cyclocondensation can be simply effected by refluxing a mixture of the enone 1 and aminoacetonitrile hydrochloride (2) in pyridine. The base
Graphical Abstract
Scheme 1: Synthesis and conversion of 3,4-dihydro-2H-pyrrole-2-carbonitriles 6.
An efficient and practical entry to 2-amido-dienes and 3-amido-trienes from allenamides through stereoselective 1,3-hydrogen shifts
- Ryuji Hayashi,
- John B. Feltenberger,
- Andrew G. Lohse,
- Mary C. Walton and
- Richard P. Hsung
Beilstein J. Org. Chem. 2011, 7, 410–420, doi:10.3762/bjoc.7.53
- -configuration. In addition, 6π-electron electrocyclic ring-closure could be carried out with 3-amido-trienes to afford cyclic 2-amido-dienes, and such electrocyclic ring-closure could be rendered in tandem with the 1,3-hydrogen shift. Keywords: allenamides; 2-amido-dienes; 3-amido-trienes; electrocyclic ring
- synthesis. As shown in Scheme 6, isomerizations of α-allylated allenamides 15a and 13 under acidic conditions can afford 3-amido-trienes 22 and 14 in excellent yields. Given the E-selectivity of this isomerization, these 3-amido-trienes are perfectly suited for thermal 6π-electron electrocyclic ring-closure
- (for reviews on pericyclic ring-closures see [83][84], for reviews on ring-closure in natural product synthesis see [85][86], for recent examples of 6π-electron electrocyclic ring-closure see [87][88][89][90][91][92][93], for examples on accelerated ring-closures of 1,3,5-hexatrienes see [94][95][96
Graphical Abstract
Scheme 1: 1,3-Hydrogen shifts of allenes.
Scheme 2: Synthesizing amido-dienes from allenamides.
Scheme 3: Synthesis of 1-amido-dienes from allenamides.
Figure 1: X-ray Structure of 10b.
Figure 2: Proposed mechanistic models.
Scheme 4: A favored pro-E TS.
Scheme 5: Unexpected competing 1,7-hydrogen shifts.
Scheme 6: Applications in pericyclic ring-closure.
Scheme 7: Cyclic 2-amido-diene synthesis.
Trapping evidence for the thermal cyclization of di-(o-acetylphenyl)acetylene to 3,3'-dimethyl- 1,1'-biisobenzofuran
- Charles P. Casey,
- Neil A. Strotman and
- Ilia A. Guzei
Beilstein J. Org. Chem. 2005, 1, No. 18, doi:10.1186/1860-5397-1-18
- coupled with a 6π electrocyclic ring closure of an o-acyl phenylcarbene (Scheme 11). This would require that the two rings be formed in planes perpendicular to one another since orthogonal orbitals of the alkyne are employed. Supporting Information Available Experimental procedures and full spectroscopic
Graphical Abstract
Scheme 1: Thermal cyclization of η2-(o-ethynylbenzoyl)rhenium complexes to rhenium isobenzofuryl carbene comp...
Scheme 2: Reagents and conditions: (a) Me3SiC≡CH, Pd(PPh3)4, CuI, Et3N, toluene, 40°C, 22 h, 99 %; (b) KF, Me...
Scheme 3: Possible thermal bicyclization of 1 to A.
Scheme 4: Thermal rearrangement of a 2,6-alkadien-4-yn-1,8-dialdehyde to a bifuran.
Scheme 5: Photochemical cyclization to a bifuran.
Scheme 6: Trapping of A by DMAD to form Diels-Alder adducts meso-3 and rac-3.
Figure 1: X-ray crystal structure of meso-3.
Scheme 7: Possible stepwise mechanism for rearrangement of 1 to A.
Scheme 8: Possible concerted mechanism for rearrangement of 1 to A.
Scheme 9: Ring closures of o-acyl phenylcarbenes to isobenzofurans.
Scheme 10: Ring opening of 2-furylcarbenes to alk-2-en-4-yn-1-ones.
Scheme 11: Coupled coarctate cyclization and 6π electrocyclization.
