Imidazoles as Hypnotic Agents. II. The Synthesis of Certain 5,6-Disubstituted 8-Oxo-8H-imidazo[5,1-c][1,4]oxazines

Godefroi, Erik F.; Eycken, Cyriel A. M. Van der; Janßen, Paul

doi:10.1021/jo01341a037

Cited by 6 publications

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“…Slow addition of the amine was required only for reactions between aliphatic amines and MPDA. Mixed glycine ester products, RN(CH 2 CO 2 Et)(CHPhCO 2 Me), were generated for the first time using an N–H insertion protocol. , In general, mechanistic studies support a stepwise mechanism with a metal–ylide intermediate, where proton transfer is simultaneous with ylide dissociation from the iridium center.…”

Section: Discussionmentioning

confidence: 99%

Iridium Porphyrin Catalyzed N–H Insertion Reactions: Scope and Mechanism

Anding

Woo

2013

Organometallics

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Ir(TTP)CH3 catalyzed N-H insertion reactions between ethyl diazoacetate (EDA) or methyl phenyldiazoacetate (MPDA) and a variety of aryl, aliphatic, primary, and secondary amines to generate substituted glycine esters with modest to high yields. Aniline substrates generally gave yields above 80%, with up to 105 catalyst turnovers, and without slow addition of the diazo reagent. Good yields were also achieved with aliphatic amines, though higher catalyst loadings and slow addition of the amine were necessary in some cases. Primary amines reacted with EDA to generate both single-and double-insertion products, either of which could be produced selectively in high yield with the proper choice of stoichiometric ratios and reaction temperature. Notably, mixed trisubstituted amines, RN(CH2CO2Et)(CHPhCO2Me), were generated from the insertion of 1 equiv of EDA and 1 equiv of MPDA into primary amines. The N-H insertion mechanism was examined using substrate competition studies, trapping experiments, and multiple spectroscopic techniques. Substrate competition studies using pairs of amines with EDA or MPDA revealed Hammett correlations with respective slopes of ρ = 0.15 and ρ+ = −0.56 as well as kinetic isotope ratios of kH/kD = 1.0 ± 0.2 and 2.7 ± 0.2. Competitive amine binding to the iridium center was demonstrated by kinetics and equilibrium binding studies. Equilibrium binding constants ranged from 102 to 105. Monitoring the reaction by absorption spectroscopy revealed a transient metalloporphyrin complex. The lifetime of this species was dependent on the nature of the amine substrate, which suggests that the catalytic cycle proceeds through a metal-ylide intermediate.

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Section: Discussionmentioning

confidence: 99%

Iridium Porphyrin Catalyzed N–H Insertion Reactions: Scope and Mechanism

Anding

Woo

2013

Organometallics

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“…They also behave as ligands in metalloenzymes and nonnatural metal complexes . Furthermore, dl -1-(1-arylalkyl)imidazole-5-carboxylic acid esters were shown to possess strong hypnotic properties . Despite the variety of synthetic approaches which are available for the construction of the imidazole ring, , imidazoles such as 4a − k bearing N -acetate or -malonate appendages are as yet difficult to prepare.…”

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confidence: 99%

“…Despite the variety of synthetic approaches which are available for the construction of the imidazole ring, , imidazoles such as 4a − k bearing N -acetate or -malonate appendages are as yet difficult to prepare. Such derivatives can be useful for the preparation of imidazo[5,1- c ]-1,4-oxazines 17b…”

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confidence: 99%

Azavinyl Azomethine Ylides from Thermal Ring Opening of α-Aziridinohydrazones: Unprecedented 1,5-Electrocyclization to Imidazoles

et al. 2007

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Michael-type addition of aziridinecarboxylates to 1,2-diaza-1,3-butadienes under solvent-free conditions (SFC) resulted in the formation of alpha-aziridinohydrazone adducts. In toluene under reflux, alpha-aziridinohydrazones gave imidazoles in moderate to good yields. Such a reactivity pattern is explained by 1,5-electrocyclization of azavinyl azomethine ylide generated through thermal ring opening of alpha-aziridinohydrazones.

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Bicyclic 5-6 Systems with One Ring Junction Nitrogen Atom: Two Extra Heteroatoms 1:1

Sliskovic¹

1996

Comprehensive Heterocyclic Chemistry II

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Imidazoles as Hypnotic Agents. II. The Synthesis of Certain 5,6-Disubstituted 8-Oxo-8H-imidazo[5,1-c][1,4]oxazines

Cited by 6 publications

References 0 publications

Iridium Porphyrin Catalyzed N–H Insertion Reactions: Scope and Mechanism

Iridium Porphyrin Catalyzed N–H Insertion Reactions: Scope and Mechanism

Azavinyl Azomethine Ylides from Thermal Ring Opening of α-Aziridinohydrazones: Unprecedented 1,5-Electrocyclization to Imidazoles

Bicyclic 5-6 Systems with One Ring Junction Nitrogen Atom: Two Extra Heteroatoms 1:1

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