Haloaziridines. 2. Synthesis and pyrolysis of some gem-dichloroaziridines

Meilahn, Marcus K.; Olsen, D.K.; Brittain, William J.; Anders, Ralph T.

doi:10.1021/jo00401a013

Cited by 34 publications

(11 citation statements)

References 2 publications

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“…63). Consistent with these findings is the observation that the 1,3-diphenyl derivative of 8 yields products resulting from a carbocationic intermediate in refluxing toluene(ε 25 = 2.4) . The stability of the carbocation formed from this compound is undoubtedly augmented by the exceptional stability conferred by the aromatic rings.…”

Section: Resultssupporting

confidence: 62%

Dramatic Effects of Halogen Substitution and Solvent on the Rates and Mechanisms of Nucleophilic Substitution Reactions of Aziridines

Banks

2008

J. Org. Chem.

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In a previous study we reported that fluorine substitution at the carbon positions of aziridine results in profound enhancements of the rate of reaction with ammonia, a typical nucleophile, in the gas phase. In this study the investigation is extended to include chloro- and bromoaziridines. Because syntheses are largely performed in the condensed phase, the present computational investigation [(MP2(Full)/6-311++G(d,p)//MP2(Full)/6-31+G(d) level] was conducted with three typical solvents that cover a wide range of polarity: THF, CH3CN, and H2O. Nucleophiles can react with haloaziridines 1 by displacing a substituted amide ion by means of an SN2 mechanism (pathway a), producing 1,2-diaminohaloethanes (from the initially formed dipolar species 2). Alternatively, a rearrangement mechanism involving rate-determining departure of a halide ion (pathway b) to form an imidoyl halide, 3, is possible. Transition-state theory was used to compute relative reaction rates of these mechanistic possibilities and to assess the role of the halogen substituents and the reaction solvent. Gas-phase results provided the basis of mechanistic insights that were more apparent in the absence of intermolecular interactions. Fluoroaziridines were found to react at accelerated rates relative to aziridine exclusively by means of the a Menshutkin-type mechanism (SN2) in each solvent tested, while the reactions of the chloro- and bromoaziridines could be directed toward 2 in the highly nonpolar solvent, cyclohexane, or toward 3 in the more polar solvents. An assessment is made of the feasibility of using this chemistry of the haloazirdines in the synthetic laboratory.

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Section: Resultssupporting

confidence: 62%

Dramatic Effects of Halogen Substitution and Solvent on the Rates and Mechanisms of Nucleophilic Substitution Reactions of Aziridines

Banks

2008

J. Org. Chem.

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“…Unfortunately, this desirable transformation is constrained by slow reaction rates and low yields . Further, side reactions of intermediate dichlorocarbene, such as disproportionation or cycloadditions to unsaturated linkages, often out-compete hydrolysis. , …”

mentioning

confidence: 99%

“…Dichlorocarbene is a known intermediate in the hydrolysis of CHCl 3 and has been shown to undergo [2 + 1]-cycloadditions with alkenes and imines to afford the corresponding cyclopropanes and aziridines. , To probe the lifetime of dichlorocarbene under these conditions, a competition experiment was carried out to afford the product 2m . As demonstrated by the 88% isolated yield and inspection of crude reaction mixtures by GC-MS, aminocarbonylation occurs selectively, even in the presence of 1.0 equiv of n -Bu 4 NBr, a phase transfer catalyst often employed to promote reactions with dichlorocarbene .…”

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confidence: 99%

Chloroform as a Carbon Monoxide Precursor: In or Ex Situ Generation of CO for Pd-Catalyzed Aminocarbonylations

2015

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Conditions for the rapid hydrolysis of chloroform to carbon monoxide (CO) using heterogeneous CsOH·H2O are described. CO and (13)CO can be generated cleanly and rapidly under mild conditions and can be captured either in or ex situ in palladium-catalyzed aminocarbonylation reactions. Utilizing only 1-3 equiv of CO allows for the aminocarbonylation of aryl, vinyl, and benzyl halides with a wide variety of primary and secondary amines giving amide products in good to excellent yields.

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“…However, its synthetic utility is severely limited due to the presence of PhHgCl, formed in the reaction. 32 To overcome this, cyclopropanation was attempted in the presence of NaI. 9 Although remarkable examples have been recorded (eq 16), the procedure lacks generality since the PhHgI formed catalyzes aziridine ring opening at rt.…”

Section: Cyclopropanation Of Alkenesmentioning

confidence: 99%