Synthesis of spiro-Annelated Isochromanones by Ring Expansion of Benzocyclobutenones in the Presence of Lithium Diisopropylphosphide

Butenschön, Holger; Kohser, Stefanie; Dongol, Krishna Gopal

doi:10.3987/com-07-s(w)11

Cited by 4 publications

(9 citation statements)

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“…In order to obtain a less electron rich derivative, we attempted to prepare the corresponding trifluoromethyl-substituted complexes rac - 7 and rac - 13 . As the direct complexation of 6-(trifluoromethyl)benzocyclobutenone failed, 1,1-diethoxy-6-(trifluoromethyl)benzocyclobutene ( 5 ) was coordinated at Cr(CO) 3 under standard reaction conditions, affording complex rac - 6 in 62% yield. Subsequent acetal hydrolysis with 50% hydrochloric acid gave the desired 6-(trifluoromethyl)benzocyclobutenone complex rac - 7 in 95% yield (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

“…In an attempt to prepare the corresponding (trifluoromethyl)-substituted benzocyclobutenedione complex rac-13, we resorted to the procedure originally reported by Liebeskind. 39 6-(Trifluoromethyl)benzocyclobutenone (8) 38 was treated with N-bromosuccinimide (NBS) under radical reaction conditions, affording 2,2-dibromo-6-(trifluoromethyl)benzocyclobutenone (9) in 46% yield. Subsequent hydrolysis with 50% sulfuric acid gave 6-(trifluoromethyl)benzocyclobutenedione (10) in 56% yield, which was transformed to the diacetal 11 in 65% yield under standard reaction conditions.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…44 C 12 H 6 CrO 6 , molecular weight 298.17 rac-Tricarbonyl[{η 6 -[1,1-diethoxy-6-(trifluoromethyl)benzocyclobutene]}chromium(0) (rac-6). 1,1-Diethoxy-6-(trifluoromethyl)benzocyclobutene (5; 38 8.00 g, 30.8 mmol) and hexacarbonylchromium (8.12 g, 36.9 mmol) in a mixture of dibutyl ether (200 mL) and THF (20 mL) were heated at reflux for 20 h. After the solution was cooled to 25 °C, it was filtered through a 5 mm thick layer of silica gel with THF as eluent. After solvent removal at reduced pressure the residue was purified by column chromatography (SiO 2 , 400 × 30 mm, TMBE/PE, 2/1), giving rac-6 (7.6 g, 19.1 mmol, 62%) as a yellow solid (mp 46 °C).…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…13 2,2-Dibromo-6-(trifluoromethyl)benzocyclobutenone (9). 6-Trifluoromethylbenzocyclobutenone (8; 8.00 g, 43.0 mmol)), 38 Nbromosuccinimide (19.14 g, 108.0 mmol), and dibenzoyl peroxide (1.3 g, 5.4 mmol) in carbon tetrachloride (200 mL) were heated at reflux for 5 days. The solution was cooled to 20 °C, and PE (100 mL) was added to precipitate the succinimide formed.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…13 C NMR [125.8 MHz, acetone-d 6 ]: δ 67.9 (CH 2 ), 68.8 (CH 2 ), 88.3 (C-6), 92.4 (d, 3 J C,F = 3.0 Hz, C-4), 92.9 (d, 2 J C,F = 39.5 Hz, C-3), 106.4 (C6a), 121.7 (C-2), 123.6 (d, 1 J C,F = 272.1 Hz, CF 3 ), 124.3 (d, 4 J C,F = 1.4 Hz, C-5), 134.8 (C-2a), 190.5 (C-1), 228.2 (CO) ppm. MS: m/z (%) 380 (13) [M + ], 352 (19) [M + − CO], 324 (16) [M + − 2CO], 296 (73) [M + − 3CO], 277 (10) [M + − 3CO − F], 268 (37) [M + − 4CO], 225 (12), 216 (17) [M + − 4CO − Cr], 196 (100) [(F 3 CC 6 H 3 Cr) + ], 172 (36), 162 (38), 155 (11), 150 (54), 144 (38), 134 (24), 125 (56), 115 (19), 106 (95) [(FCC 6 H 3 ) + ], 103 (50), 87 (78) [C 7 H 3 ) + ], 75 (53) Unsuccessful Attempts toward 1,1,2,2-Tetramethoxy-3-(trifluoromethyl)benzocyclobutene (32). (a) At 0 °C trimethoxymethane (0.6 mL, 5.0 mmol) was added to 6-(trifluoromethyl)benzocyclobutenedione (10; 0.10 g, 0.5 mmol) in methanol (1 mL).…”

Section: ■ Experimental Sectionmentioning

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: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Experimental Sectionmentioning

confidence: 99%

Section: ■ Experimental Sectionmentioning

confidence: 99%

Section: ■ Experimental Sectionmentioning

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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ChemInform Abstract: Synthesis of spiro Anellated Isochromanones by Ring Expansion of Benzocyclobutenones in the Presence of Lithium Diisopropylphosphide.

2008

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The Influence of Phosphorus Substituents on the Structures and Solution Speciation of Trivalent Uranium and Lanthanide Phosphinodiboranates

Zgrabik,

Bhowmick,

Eckstrom

et al. 2023

Inorg. Chem.

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Here, we report the mechanochemical synthesis and characterization of homoleptic uranium and lanthanide phosphinodiboranates with isopropyl and ethyl substituents attached to phosphorus. M(H 3 BP i Pr 2 BH 3 ) 3 complexes with M = U, Nd, Sm, Tb, and Er were prepared by ball milling UI 3 (THF) 4 , SmBr 3 , or MI 3 with three equivalents of K(H 3 BP i Pr 2 BH 3 ). M(H 3 BPEt 2 BH 3 ) 3 with M = U and Nd were prepared similarly using K(H 3 BPEt 2 BH 3 ), and the complexes were purified by extraction and crystallization from Et 2 O or CH 2 Cl 2 . Single-crystal XRD studies revealed that all five M(H 3 BP i Pr 2 BH 3 ) 3 crystallize as dimers, despite the significant differences in metal radii across the series. In contrast, Nd(H 3 BPEt 2 BH 3 ) 3 with smaller ethyl substituents crystallized as a coordination polymer. Crystals of U(H 3 BPEt 2 BH 3 ) 3 were not suitable for structural analysis, but crystals of U(H 3 BPMe 2 BH 3 ) 3 isolated in low yield by solution methods were isostructural with Nd(H 3 BPEt 2 BH 3 ) 3 . 1 H and 11 B NMR studies in C 6 D 6 revealed that all of the complexes form mixtures of monomer and oligomers when dissolved, and the extent of oligomerization was highly dependent on metal radius and phosphorus substituent size. A comprehensive analysis of all structurally characterized uranium and lanthanide phosphinodiboranate complexes reported to date, including those with larger Ph and t Bu substituents, revealed that the degree of oligomerization in solution can be correlated to differences in B−P−B angles obtained from single-crystal XRD studies. Density functional theory calculations, which included structural optimizations in combination with conformational searches using tight binding methods, replicated the general experimental trends and revealed free energy differences that account for the different solution and solid-state structures. Collectively, these results reveal how steric changes to phosphorus substituents significantly removed from metal coordination sites can have a significant influence on solution speciation, deoligomerization energies, and the solid-state structure of homoleptic phosphinodiboranate complexes containing trivalent f-metals.

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Synthesis of spiro-Annelated Isochromanones by Ring Expansion of Benzocyclobutenones in the Presence of Lithium Diisopropylphosphide

Cited by 4 publications

References 7 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

ChemInform Abstract: Synthesis of spiro Anellated Isochromanones by Ring Expansion of Benzocyclobutenones in the Presence of Lithium Diisopropylphosphide.

The Influence of Phosphorus Substituents on the Structures and Solution Speciation of Trivalent Uranium and Lanthanide Phosphinodiboranates

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