Isotopic Exchange between D<sub>2</sub>O and NaBH<sub>4</sub>

Girardot, Peter R.; Parry, R. W.

doi:10.1021/ja01149a522

Cited by 12 publications

(2 citation statements)

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“…Because the endergonic formation of Int2” (relative to 1 + MeOD) occurs via easily accessible barriers, it can be implied from the principle of microscopic reversibility that deprotonation of the B-bound η 2 -H 2 fragment of Int2” by methoxide would result in deuteration of BH 4 – ( 1 ); indeed, upon dissolution of NaBH 4 in CD 3 OD (see the Experimental Section of the Supporting Information), in ∼15 min, a characteristic 1:1:1 triplet (δ B = −43.4 ppm, 1 J B‑D = 12.50 Hz) corresponding to BH 3 D – was observed in the 11 B{ 1 H} NMR spectrum (Figure b). Although the preparation of NaBH n D (4– n ) by the reaction of 1 with D 2 O has been previously reported, , the reaction had not been mechanistically corroborated.…”

Section: Resultsmentioning

confidence: 92%

Protonolysis of BH₄^– Leads to Intermediacy of BH₃-σ(H₂) That Evolves H₂ and Furnishes Borane as the Key Reducing Agent

Pal

2023

Organometallics

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Borohydride (BH 4 − ) is a ubiquitous reducing agent in chemistry despite its apparent inability to transfer hydride fragments without assistance. In protic solvents such as methanol, B−H protonolysis and H 2 evolution furnish borane, which serves as the key hydride delivery agent in the reduction of cyclohexanone. Contrasting with widely accepted but inaccessible mechanisms involving direct (intermolecular) hydride transfer from BH 4 − , in this work, DFT calculations performed in close conjunction with H/D exchange studies unambiguously justify the use of alcohol as a necessary evil that renders substantial kinetic advantages in intramolecular hydride transfer, albeit requiring excess BH 4 − to compensate for the protonolytic loss of available B−H fragments as H 2 .

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Section: Resultsmentioning

confidence: 92%

Protonolysis of BH₄^– Leads to Intermediacy of BH₃-σ(H₂) That Evolves H₂ and Furnishes Borane as the Key Reducing Agent

Pal

2023

Organometallics

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“…The solvent was evaporated, and the residue was chromatographed on alumina by the dry column technique. 16 Elution with benzene produced a yellow band near the top of the column, and this was cut out and extracted with benzene. Evaporation of the benzene gave a brown solid, which was crystallized from 95% ethanol-Skelly B solvent.…”

mentioning

confidence: 99%

Synthesis of 2-methylpiperidine-2-d. Choice of reductive methods from azomethine precursors

Craig¹,

Lee²

1975

J. Org. Chem.

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N-(2-Phenethyl)-3,5-diphenylpyrrole-2-carboxamide (7). A mixture of 6.30 g (0.022 mol) of ethyl 2,4-diphenylpyrrole-5-carboxylate and 8.47 g (0.070 mol) of 6-phenethylamine was heated at 240-250O for 8 hr. The dark brown liquid was cooled to room temperature and then induced to deposit crystals by addition of small amounts of ether and Skelly B solvent. The solid was washed with ether and crystallized from 95% ethanol to give 2.80 g (35%) of 7: mp 177-179'; ir (CHC13) 3435 (NH), 1627 (amide C=O) cm-l; nmr (CDC13) 6 2.68 (t, 2 H, J = 6.7 Hz), 3.52 (4, 2 H, J = 6.7 Hz), 5.85 (t, broad, 1 H), 6.49 (d, 1 H, J = 3 Hz), 6.9-7.8 (m, 15 H), 10.55 (s, broad, 1 H).Anal. Calcd for C25HzzNz0: C, 81.93; H, 6.05; N, 7.65. Found: C, 82.14; H, 6.04; N, 7.60. 2-(3,4-Dihydro-l-isoquinolyl)-3,5-diphenylpyrrole (8). A mixture of 1.0 g (2.7 mmol) of 7 and 10 g of phosphorus pentoxide in 15 ml of anhydrous p-xylene was heated under reflux for 6 hr. The hot p-xylene layer was decanted from a black, insoluble residue. The residue was added to 600 ml of ice-cold water with stirring, and a brown solid which formed was collected by filtration, washed with water, and suspended in concentrated sodium hydroxide solution. The suspension was diluted with water and then neutralized with G N sulfuric acid. The mixture was extracted with benzene, and the benzene extract was washed with water and dried over anhydrous magnesium sulfate. The solvent was evaporated, and the residue was chromatographed on alumina by the dry column technique.ls Elution with benzene produced a yellow band near the top of the column, and this was cut out and extracted with benzene. Evaporation of the benzene gave a brown solid, which was crystallized from 95% ethanol-Skelly B solvent. A crystalline product of mp 209-211O was recrystallized from acetone to give 0.20 g (21%) of 8: mp 214-216'; ir (CHC13) 3440 (NH), 1601(C=N) cm-l; nmr (CDC13) 6 2.70 (t, 2 H, J = 7 Hz), 3.60 (t, 2 H, J

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Metal Tetrahydroborates

James

Wallbridge

1970

Progress in Inorganic Chemistry

121

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Isotopic Exchange between D₂O and NaBH₄

Cited by 12 publications

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Protonolysis of BH₄^– Leads to Intermediacy of BH₃-σ(H₂) That Evolves H₂ and Furnishes Borane as the Key Reducing Agent

Protonolysis of BH₄^– Leads to Intermediacy of BH₃-σ(H₂) That Evolves H₂ and Furnishes Borane as the Key Reducing Agent

Synthesis of 2-methylpiperidine-2-d. Choice of reductive methods from azomethine precursors

Metal Tetrahydroborates

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Isotopic Exchange between D2O and NaBH4

Cited by 12 publications

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Protonolysis of BH4– Leads to Intermediacy of BH3-σ(H2) That Evolves H2 and Furnishes Borane as the Key Reducing Agent

Protonolysis of BH4– Leads to Intermediacy of BH3-σ(H2) That Evolves H2 and Furnishes Borane as the Key Reducing Agent

Synthesis of 2-methylpiperidine-2-d. Choice of reductive methods from azomethine precursors

Metal Tetrahydroborates

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Product

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Isotopic Exchange between D₂O and NaBH₄

Protonolysis of BH₄^– Leads to Intermediacy of BH₃-σ(H₂) That Evolves H₂ and Furnishes Borane as the Key Reducing Agent

Protonolysis of BH₄^– Leads to Intermediacy of BH₃-σ(H₂) That Evolves H₂ and Furnishes Borane as the Key Reducing Agent