New synthesis of α-acyl imines by radical-mediated group-transfer imidoylation of acyl tellurides with isonitriles

Yamago, Shigeru; Miyazoe, Hiroshi; Sawazaki, Takashi; Goto, Ryuta; Yoshida, Jun‐ichi

doi:10.1016/s0040-4039(00)01287-9

“…Because of their availability and the parallel reactivity of chalcogen group transfer reactions with halogen atom transfer reactions, we selected organotellurium compounds as precursors for carbon-centered radicals. , In this work, we found the first example of the group-transfer imidoylation of organotellurium compounds with isonitriles, as shown in eq 3. Preliminary results have already been reported . We now report the full details of this study, together with experimental and theoretical studies, to elucidate the origin of the reactivity difference between isonitriles and CO.…”

Section: Introductionmentioning

confidence: 73%

Synthetic and Theoretical Studies on Group-Transfer Imidoylation of Organotellurium Compounds. Remarkable Reactivity of Isonitriles in Comparison with Carbon Monoxide in Radical-Mediated Reactions

Yamago

¹

,

Miyazoe

²

,

Goto

³

et al. 2001

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Imidoylation of organotellurium compounds with isonitriles has been investigated in conjunction with the radical-mediated C1 homologation reaction by using CO and isonitriles. Carbon-centered radicals generated photochemically or thermally from organotellurium compounds react with isonitriles in a group-transfer manner to give the corresponding imidoylated products. Organotellurium compounds have been found to serve as effective precursors of a wide variety of stabilized radicals, namely benzyl, alpha-alkoxy, alpha-amino, and acyl radicals, which take part in the imidoylation with high efficiency. The reactions are compatible with various functional groups, and can be carried out in various solvents including environmentally benign water. The reactivity of isonitriles has been compared with that of CO through competition experiments, and the results indicate that isonitriles are superior to CO as radical acceptors in reactions with stabilized radicals. The origin of the differences has been addressed in theoretical studies with density functional theory calculations using the B3LYP hybrid functional. The calculations suggest that both carbonylation and imidoylation proceed with low activation energies, and that there are virtually no differences in the kinetic sense. Instead, it indicates that thermodynamic effects, namely differences in the stability of the acyl and the imidoyl radicals, control the overall course of the reactions.

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“…On the basis of our discovery of reversible radical generation from organotellurium compounds via carbon−tellurium bond thermolysis and photolysis, , we developed new organotellurium-group-transfer radical-coupling reactions. − During the course of our investigations, we discovered that several organotellurium compounds were excellent CTAs for LRP. ,, Furthermore, we recently found that organostibines and organobismuthines also promote highly controlled LRP. These methods are versatile and produce a variety of well-defined polymers with several different functional groups.…”

Section: Introductionmentioning

confidence: 99%

Precision Polymer Synthesis by Degenerative Transfer Controlled/Living Radical Polymerization Using Organotellurium, Organostibine, and Organobismuthine Chain-Transfer Agents

Yamago

¹

2009

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“…Yamago, Yoshida and coworkers reported that at elevated temperature, acyl tellurides can undergo a radical-mediated group transfer with isonitriles, generating α-acyl substituted imidoyl tellurides in good to high yields. 85 In 2013, MacMillan and coworkers applied the radical chemistry of acyl tellurides to generate the challenging seven-membered azepanyl ring system in (-)-vincorine ( Figure 6c). 86 Therein, the researchers evaluated various radical precursors, such as the Barton ester and selenoesters, but ultimately found that upon thermal initiation, the acyl telluride precursor (101) generated the desired azepanyl allene (102) most efficiently.…”

Section: Telluriummentioning

confidence: 99%

“…Yamago, Yoshida and coworkers reported that at elevated temperature, acyl tellurides can undergo a radical-mediated group transfer with isonitriles, generating α-acyl substituted imidoyl tellurides in good to high yields. 85 In 2013, MacMillan and coworkers applied the radical chemistry of acyl tellurides to generate the challenging seven-membered azepanyl ring system in (−)-vincorine ( Fig. 6c ).…”

Section: Telluriummentioning

confidence: 99%