The Reaction of Organoboranes with Ethyl P-Nitrobenzenesulfonoxy-Carbamate Under Two-Phase Conditions. A Convenient Synthesis of Ethyl N-Alkylcarbamates from Olefins via Hydroboration

AKIMOTO, I.; Suzuki, Akira

doi:10.1080/00397918108061879

Cited by 23 publications

(4 citation statements)

References 15 publications

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“…Ethyl nosyloxycarbamate reacts with cyclohexene in the presence of Et 4 NF in MeCN, giving the corresponding aziridine in 14% yield (Scheme 5), or, as reported by Akimoto et al, with organoboranes. This represents a convenient synthesis of ethyl N-alkyl carbamates from olefins, via hydroboration (Scheme 6) [26]. Lukevics et al used betaines derived from amino and hydrazino acids as phase-transfer catalysts [27].…”

Section: Introductionmentioning

confidence: 99%

Ethyl Nosyloxycarbamate: A Chameleonic Aminating Agent

Pellacani¹,

Fioravanti²,

Tardella

2011

COC

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The purpose of this review is to illustrate the use of ethyl nosyloxycarbamate (NsONHCO(2)Et). This is a versatile aminating agent known for over 47 years and used to generate, in the presence of organic or inorganic bases under homogeneous conditions, a carbonyl nitrene, a reactive intermediate able to form new C-N or X-N bonds by electrophilic amination reaction of a remarkable variety of nucleophilic substrates. Interest in this reagent has been renewed most recently, during the past dozen years. Operating still in alkaline medium, but under generally heterogeneous conditions, has made possible new synthetic applications for the conjugate base of the same nosyloxycarbamate. These, developed mainly by our research group, allow to carry out direct syntheses of various nitrogenated compounds under mild conditions. The applications span from simple molecules to highly functionalized compounds and many new exciting regio- and stereoselective routes can be envisioned. In particular, it was possible to obtain aziridines containing a cornucopia of assorted functions and therefore able to provide access to more complex molecules under simple operational conditions by using an aminating agent cheap and easy to obtain

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Section: Introductionmentioning

confidence: 99%

Ethyl Nosyloxycarbamate: A Chameleonic Aminating Agent

Pellacani¹,

Fioravanti²,

Tardella

2011

COC

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“…The generation of 2V-carbethoxynitrene by a-elimination and trapping with a triorganoborane is best conducted in a two-phase system with a quaternary ammonium chloride [Akimoto, 1981].…”

Section: Chrmentioning

confidence: 99%

Phase Transfer Reactions

Ho¹

1998

Distinctive Techniques for Organic Synthesis

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Chemical reactions involving two or more molecules usually proceed at higher rates in one phase. However, it is not always feasible or expedient to render some reactions under homogeneous conditions. In such cases the phase transfer technique should be considered. Improvement of reactions by phase transfer catalysis (PTC) represents a breakthrough in chemical technology. Although sporadic reports appeared before the 1960s, consolidation of the concept through a series of publications on the theme of extractive alkylation [Markosza, 1965], a patent describing catalysis of heterogeneous reactions [Starks, 1968], and the observations concerning reactions of quaternary ammonium salts in nonpolar media [Brandstrom, 1969[Brandstrom, , 1972 initiated an avalanche of research in the methodology.While the most common phase transfer technique deals with reactants in two immiscible liquids, its scope encompasses gas-liquid, gas-solid, liquid-solid, and presumably solid-solid systems. In comparison with conventional methods, PTC holds considerable advantages in terms of cost (which avoids expensive anhydrous dipolar aprotic solvents), time, mildness, and simplicity. It is often observed that reactivities and selectivities are enhanced under such conditions.From an electrochemical study [Tan, 1994] of the Williamson ether synthesis under phase transfer catalysis, it is concluded that the role of the catalyst is to establish a Galvani distribution potential difference between the two phases which acts as the driving force for transferring the reactive ions from the aqueous medium to the organic layer.The general features of a typical PTC substitution reaction carried out in a system of organic and aqueous phases specifies reaction taking place in the organic layer. The phase transfer agent is present in catalytic amount and capable of moving one reactant in its resident solvent into that of the other reactant or the interfacial region. Only then the two species can react with reasonable speed. Needless to say that strong agitation is a most crucial to maximize reaction rates.Actually there are two mechanistic models for the PTC reaction. In the Starks extraction mechanism the catalyst is biphilic, thus well qualified by a quaternary ammonium or phosphonium salt, either of which having finite solubility in both phases on account of its charge and organophilicity, capable of ferrying the counter anion from the aqueous phase to the organic layer by the partition phenomenon. The 1 Distinctive Techniques for Organic Synthesis Downloaded from www.worldscientific.com by PURDUE UNIVERSITY on 04/13/15. For personal use only.2 Distinctive Techniques for Organic Synthesis anion generated from reaction will pair with the quaternary onium species and enter the aqueous phase and a second catalytic cycle starts at this point. The interfacial mechanism (proposed by Makosza and modified by Brandstrom and Montanari) describes cases in which the catalyst is highly organophilic and it functions by anion exchange in the interfacial region. In ot...

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“…Despite these recent advances in the synthesis of amines from alkenes, there are a number of limitations. Particularly relevant to the work we report, methods for the synthesis of secondary amines from alkenes are limited to isolated examples, and these reactions occurred in low yield (Scheme b). − In addition, the utility of reactions to form primary amines is limited by the properties of the reagent used for amination. Hydrazoic acid has been used as the reagent to provide primary amines from alkylboron reagents in high yields, but the explosion hazard of hydrazoic acid limits the utility of this method.…”

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confidence: 99%