Tricarbonyl(3-methoxybenzocyclobutenedione)chromium: Regioselective Nucleophilic Addition Reactions, Dianionic Oxy-Cope Rearrangements, Regioselective Intramolecular Aldol Additions, and a Rare Case of an Anionic 1-Vinylcyclobutenol−Cyclohexadienol Rearrangement

Dongol, Krishna Gopal; Wartchow, Rudolf; Butenschön, Holger

doi:10.1002/1099-0690(200206)2002:12<1972::aid-ejoc1972>3.0.co;2-h

Cited by 19 publications

(11 citation statements)

References 12 publications

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“…In both compounds the rather long bond length C1–C2 ( 2 , 156.6 pm; rac - 4 , 156.1 pm) causes the annelated ring to adopt a distorted-rectangular geometry. As in 3 and in rac - 16 , the methoxy substituent adopts a conformation with the methyl group directed to the keto function. This conformation is presumably preferred for electrostatic reasons, because the lone electron pairs of the methoxy and those of the keto oxygen atoms point away from each other.…”

Section: Resultsmentioning

confidence: 96%

“…While the crystal structure analysis of rac - 16 has already been reported, here a structure analysis of the closely related rac - 14 has been performed, which was crystallized from dichloromethane/hexane (Figure ). A comparison of relevant structural parameters is given in Table .…”

Section: Resultsmentioning

confidence: 99%

“…Within our investigations in the field of (arene)tricarbonylchromium complexes we concentrated on ligand systems with annelated functionalized rings. As results of this research a number of oxyanion accelerated reactions which take place at low temperatures, starting from the tricarbonylchromium complexes rac - 1 and 2 of benzocyclobutenone and benzocyclobutenedione (Scheme ), were disclosed. − These include the anion-driven ring opening of benzocyclobutenol complexes to the corresponding o -quinodimethane intermediates, which can be trapped by [4 + 2] cycloadditions or electrocyclic processes, − and the dianionic oxy-Cope rearrangement, which occurs upon nucleophilic syn diaddition of alkenyllithium reagents at 2 . − More recently, we found the first examples of an anionic thia-Fries rearrangement at (arene)tricarbonylchromium complexes. , …”

Section: Introductionmentioning

confidence: 99%

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Trifluoromethyl-Substituted Benzocyclobutenone and Benzocyclobutenedione: The Structure Anomaly of (Benzocyclobutenedione)tricarbonylchromium Complexes

et al. 2019

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The syntheses of methoxy- and trifluoromethyl-substituted benzocyclobutenone and benzocyclobutenedione tricarbonylchromium complexes are described. As with the unsubstituted complex, a route via the respective acetals was used. However, attempts to hydrolyze rac-tricarbonyl[1,2-bis(ethylenedioxy)-3-(trifluoromethyl)benzocyclobutene]chromium(0) (rac-12) resulted in only a single hydrolysis and led to rac-tricarbonyl{η6-[2-(ethylendioxy)-3-(trifluoromethyl)benzocyclobutenone]}chromium(0) (rac-14) with different regioselectivity in comparison to the respective reaction of the methoxy-substituted derivative. The synthesis of the desired rac-tricarbonyl[3-(trifluoromethyl)benzocyclobutenedione]chromium(0) (rac-13) was finally achieved by a route via an acyclic diacetal. Compounds were characterized spectroscopically and in a number of cases also by crystal structure analyses. The unusual bending of the annelated cyclobutenedione ring toward the tricarbonylchromium moiety was observed for rac-tricarbonyl-[η6-(methoxybenzocyclobutenedione)chromium(0) (rac-4) as well. To gain more insight into the unusually large bending of the annelated cyclobutenedione or cyclobutenone rings toward the tricarbonylchromium group in some of the studied compounds, we also performed density functional theory (DFT) calculations. In general, the gas-phase DFT optimized structure parameters show good agreement with the crystal structure data, indicating that the cyclobutenedione or cyclobutenone ring bending is a molecular rather than a crystal-packing effect. The DFT optimized structure data also show that annelated cyclobutenedione rings bend more strongly toward the tricarbonylchromium group than do their cyclobutenone analogues. Moreover, the staggered conformation of the tricarbonylchromium group favors larger bending angles. Topological analyses of the electron density of the studied (arene)tricarbonylchromium complexes suggest that the cyclobutenedione ring bending originates from the bending of π orbitals of the arene ring toward the tricarbonylchromium group.

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Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Trifluoromethyl-Substituted Benzocyclobutenone and Benzocyclobutenedione: The Structure Anomaly of (Benzocyclobutenedione)tricarbonylchromium Complexes

et al. 2019

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“…As part of our research into (arene)tricarbonylchromium complexes with functionalized annellated rings, we have found that benzocyclobutenedione complexes such as 4 undergo syn diaddition reactions with vinyllithium followed by dianionic oxy‐Cope rearrangements to give benzocyclooctenedione complexes 5 or the respective products of subsequent intramolecular aldol addition reactions after hydrolytic work‐up (Scheme ). These reactions are remarkable in that they take place immediately at low reaction temperatures (–78 °C) in high yields . Related anti diaddition reactions of vinylmetals to squaric acid esters followed by anion‐driven rearrangements were reported by Paquette …”

Section: Introductionmentioning

confidence: 82%

Dianionic Oxy‐Cope Rearrangement with Benzil Derivatives: meso‐Selective 3,3‐Coupling of Two Tetrahydrofuran Moieties

et al. 2017

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Benzil and its derivatives naphthil and pyridil have been found to undergo a dianionic oxy‐Cope rearrangement upon reaction with 2‐lithio‐4,5‐dihydrofuran to give 3,3′‐octahydrobifuranyls selectively as the meso diastereomers. The diastereoselectivity is explained based on the reaction mechanism and the conformation of the starting material. 4,4′‐Di‐tert‐butylbenzil gave the respective intramolecular aldol adduct, whose relative configuration was determined by NOE experiments.

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“…This can facilitate the transfer of the planar chirality of the chromium complex to a center of chirality in the annellated ring. Butenschön and coworkers 165 utilized this synthetic protocol to study dianionic oxy-Cope rearrangements. In contrast to the dianionic oxy-Cope rearrangements starting from the unsubstituted benzocyclobutenedione complex which afforded symmetrical bis(enolates), treatment of 395 with a vinyllithium provided bis(enolate) 396 as a result of the rearrangement process.…”

Section: B Cope Rearrangementmentioning

confidence: 99%

The Application of Cyclobutane Derivatives in Organic Synthesis

Chan

2009

Patai's Chemistry of Functional Groups

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Tricarbonyl(3-methoxybenzocyclobutenedione)chromium: Regioselective Nucleophilic Addition Reactions, Dianionic Oxy-Cope Rearrangements, Regioselective Intramolecular Aldol Additions, and a Rare Case of an Anionic 1-Vinylcyclobutenol−Cyclohexadienol Rearrangement

Cited by 19 publications

References 12 publications

Trifluoromethyl-Substituted Benzocyclobutenone and Benzocyclobutenedione: The Structure Anomaly of (Benzocyclobutenedione)tricarbonylchromium Complexes

Trifluoromethyl-Substituted Benzocyclobutenone and Benzocyclobutenedione: The Structure Anomaly of (Benzocyclobutenedione)tricarbonylchromium Complexes

Dianionic Oxy‐Cope Rearrangement with Benzil Derivatives: meso‐Selective 3,3‐Coupling of Two Tetrahydrofuran Moieties

The Application of Cyclobutane Derivatives in Organic Synthesis

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