Preparation and characterization of crystalline N-acylammonium salts

King, J.; Bryant, G. L.

doi:10.1021/jo00045a025

Cited by 52 publications

(23 citation statements)

References 3 publications

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“…[22] In order to probe the feasibility of such a process, we synthesized the easily accessible acyl-pyridinium salt 9 (Scheme 5). [23] This stable compound shows no reactivity toward PO and CO. Also PPN[Co(CO) 4 ] [24] alone does not react with PO and CO ( À and PHB as in the case of pyridine addition (Figure 2) appear in the ATR-IR spectrum, indicating the occurrence of the same chemistry.…”

Section: Resultsmentioning

confidence: 99%

Mechanistic Aspects of the Metal Catalyzed Alternating Copolymerization of Epoxides and Carbon Monoxide

Allmendinger¹,

Molnár

Zintl³

et al. 2005

Chemistry A European J

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The cobalt-catalyzed alternating copolymerization of epoxides and CO is a novel, direct approach to aliphatic polyesters, such as poly(hydroxybutyrate) (PHB). This reaction was found to be catalyzed by Ph3Si[Co(CO)4] (4) and pyridine affording in a first step the stable mono-insertion product Ph3Si-O-CH(CH3)-CH2-CO-Co(CO)4 (5). However, a profound mechanistic understanding, especially of the role of pyridine as the key component for the polymerization reaction was missing. ATR-IR online monitoring under catalytic conditions and DFT calculations were used to show that an acylpyridinium cation is formed by cleavage of the cobalt-acyl bond of 5 in the presence of pyridine. The Lewis acid thus generated activates the next incoming epoxide monomer for ring opening through [Co(CO)4]-. The catalytic cycle is completed by a subsequent CO insertion in the new cobalt-alkyl bond. The calculations are used to explore the energetic hypersurface of the polymerization reaction and are complemented by extended experimental investigations that also support the mechanistic hypotheses.

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Section: Resultsmentioning

confidence: 99%

Mechanistic Aspects of the Metal Catalyzed Alternating Copolymerization of Epoxides and Carbon Monoxide

Allmendinger¹,

Molnár

Zintl³

et al. 2005

Chemistry A European J

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“…N -Carbophenoxypyridinium tetraphenylborate ( 6 ) was prepared by the method of King14 and recrystallized from CH 2 Cl 2 –Et 2 O. N -Benzylidenepyrrolidinium tetrafluoroborate ( 11 ),40 Cp*Ru(dppf)H ( 5 ),26 CpRu(dppf)H ( 3 ),41 Cp*Ru(dppe)H ( 4 ),29 and CpRu(dppe)H ( 2 )42 were prepared by the literature methods. CD 2 Cl 2 and CD 3 CN were degassed and stored over 3 Å molecular sieves.…”

Section: Methodsmentioning

confidence: 99%

“…13 In the present work we have investigated the reactivity of the Ru hydride complexes 2 – 5 toward the acyl pyridinium cation 6 ,14 and the ability of 5 to catalyze the hydrogenation of 6 . The water-soluble Ru catalyst 7 and the Rh catalyst 8 have been shown to catalyze the 1,4 hydrogenation of NAD + models as well as NADP + 15–17…”

Section: Introductionmentioning

confidence: 99%

Using a Two-Step Hydride Transfer To Achieve 1,4-Reduction in the Catalytic Hydrogenation of an Acyl Pyridinium Cation

et al. 2008

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The stoichiometric reduction of N-carbophenoxypyridinium tetraphenylborate (6) by CpRu(P-P)H (Cp = η 5 -cyclopentadienyl; P-P = dppe, 1,2-bis(diphenylphosphino)ethane or dppf, 1,1′-bis (diphenylphosphino)ferrocene) and Cp*Ru(P-P)H (Cp* = η 5 -pentamethylcyclopentadienyl; P-P = dppe) gives mixtures of 1,2-and 1,4-dihydropyridines. The stoichiometric reduction of 6 by Cp*Ru (dppf)H (5) gives only the 1,4-dihydropyridine, and 5 catalyzes the exclusive formation of the 1,4-dihydropyridine from 6, H 2 , and 2,2,6,6-tetramethylpiperidine. In the stoichiometric reductions, the ratio of 1,4 to 1,2 product increases as the Ru hydrides become better one-electron reductants, suggesting that the 1,4 product arises from a two-step (e − /H•) hydride transfer. Calculations at the UB3LYP/6-311++G(3df,3pd)//UB3LYP/6-31G* level support this hypothesis, indicating that the spin density in the N-carbophenoxypyridinium radical (13) resides primarily at C4, while the positive charge in 6 resides primarily at C2 and C6. The isomeric dihydropyridines thus result from the operation of different mechanisms: the 1,2 product from a single-step H − transfer and the 1,4 product from a two-step (e − /H•) transfer.

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“…The crystal structure determination of (I) forms part of our continuing work on aryl carbonates (King & Bryant, (1) 1990, 1992. There is a great deal of interest in the crystal structures of chloroformates (Exner & Fiedler, 1987;O'Gorman, Shand & Schomaker, 1950;Robinson, 1953;Wanner, Praschak & Nagel, 1990).…”

Section: Commentmentioning

confidence: 99%