Transition metal-catalyzed aminocarbonylation of aryl halides with CO and amines, pioneered by Heck and co-workers in the 1970s, is among the most commonly employed reactions to make aromatic amides. A catalyst-free aminocarbonylation of aryl iodides with CO and amines, which simply uses photoirradiation conditions by Xe-lamp, has now been developed. This methodology shows broad functional-group tolerance, including that of heteroaromatic amides. A hybrid radical/ionic chain mechanism, involving electron transfer from zwitterionic radical intermediates generated by nucleophilic attack of amines to aroyl radicals, is proposed.
Palladium-Catalyzed Carbonylative Couplings of Vinylogous Enolates: Application to Statin Structures IIya S. Makarov, Takashi Kuwahara, Xavier Jusseau, Ilhyong Ryu, Anders T. Lindhardt, Troels Skrydstrup J. Org. Chem, 2015, 137, 44 pp. 14043 - 14046 DOI: 10.1021/jacs.5b09342
The first Pd-catalyzed carbonylative couplings of aryl and vinyl halides with vinylogous enolates are reported generating products derived from C–C bond formation exclusively at the γ-position. Good results were obtained with a dienolate derivative of acetoacetate (1,3-dioxin-4-one). These transformations occurred at room temperature and importantly with only stoichiometric carbon monoxide in a two-chamber reactor. The methodology was applied to the synthesis of two members of the statin family generating the cis-3,5-diol acid motif by a γ-selective carbonylation followed by a cis-stereoselective reduction of the 3,5-dicarbonyl acid intermediates.
Carbonylative Mizoroki–Heck Reaction of Alkyl Iodides with Arylalkenes Using a Pd/Photoirradiation System Shuhei Sumino, Takahito Ui, Yuki Hamada, Takahide Fukuyama, Ilhyong Ryu Org. Lett., 2015, 17, 20 pp. 4952 - 4955 DOI: 10.1021/acs.orglett.5b02302
A carbonylative Mizoroki–Heck reaction using alkyl iodides was achieved with a Pd/photoirradiation system using DBU as a base. In this reaction, alkyl radicals were formed from alkyl iodides via single-electron transfer (SET) and then underwent a sequential addition to CO and alkenes to give β-keto radicals. It is proposed that DBU would abstract a proton α to carbonyl to form radical anions, giving α,β-unsaturated ketones via SET.
Intramolecular Carbolithiation of 3-Lithioxy-5-alkenyllithiums as a Platform for Cyclopentanols and Cyclopentanones Ilhyong Ryu, Go-hei Yamamura, Satoshi Minakata, Mitsuo Komatsu, Haruka Kubo, Mitsuhiro Ueda Synlett, 2015, 26, pp. 2413 - 2417 DOI: 10.1055/s-0035-1560170
Intramolecular carbolithiation of 3-lithioxy-5-hexenyllithiums was studied. Unlike the case of 5-hexenyllithium, the cyclization of 3-lithioxy-5-hexenyllithium was very sluggish. Acceleration was observed when lithium chloride was added, suggesting that intramolecular lithioxy coordination would hinder the cyclization. Introduction of a silyl or thiophenyl group at the olefin terminus caused smooth cyclization. The resulting dianions having a cyclopentane framework are subjected to C–C bond-forming reaction with electrophiles to give 3-substituted cyclopentanols. Coupled with the Swern oxidation, the overall protocol served as a platform for 3-substituted cyclopentanones.
Photocatalytic One-Pot Synthesis of Homoallyl Ketones via a Norrish Type I Reaction of Cyclopentanones Megumi Okada, Keiichi Yamada, Takahide Fukuyama, Davide Ravelli, Maurizio Fagnoni, Ilhyong Ryu J. Org. Chem, 2015, 80, 18 pp. 9365 - 9369 DOI: 10.1021/acs.joc.5b01850
A photocatalytic synthesis of homoallyl ketones was achieved via a one-pot procedure starting from a Norrish Type I reaction of cyclopentanones, followed by a decatungstate-catalyzed hydroacylation of electron-deficient olefins by the resulting 4-pentenals. The site-selective formyl H-abstraction in the second step can be explained by radical polar effects in the transition state.
Coupling-Reagent-Free Synthesis of Dipeptides and Tripeptides Using Amino Acid Ionic Liquids Shinya Furukawa , Takahide Fukuyama, Akihiro Matsui, Mai Kuratsu, Ryotaro Nakaya, Takashi Ineyama, Hiroshi Ueda, Ilhyong Ryu Chem. Eur. J., 2015, 21, 34 pp. 11980 - 11983 DOI: 10.1002/chem.201501783
A general method for the synthesis of dipeptides has been developed, which does not require any coupling reagents. This method is based on the reaction of readily available HCl salts of amino acid methyl esters with tetrabutylphosphonium amino acid ionic liquids. The isolation procedure of stepwise treatment with AcOH is easy to carry out. The method was extended to the synthesis of tripeptide, tyrosyl-glycyl-glycine, present in IMREG-1, also.
Synthesis of aromatic β-keto esters via a carbonylative Suzuki–Miyaura coupling reaction of α-iodo esters with arylboronic acids Shuhei Sumino, Takahito Ui, Ilhyong Ryu Org. Chem. Front, 2015, 2, 9 pp. 1085 - 1087 DOI: 10.1039/C5QO00185D
Aromatic β-keto esters were synthesized via a carbonylative cross-coupling reaction of alkyl iodides and arylboronic acids in the presence of a catalytic amount of Pd catalyst. A cooperative radical and Pd-catalyzed mechanism is proposed.
Photocatalyzed Site-Selective C–H to C–C Conversion of Aliphatic Nitriles Keiichi Yamada, Megumi Okada, Takahide Fukuyama, Davide Ravelli, Maurizio Fagnoni, Ilhyong Ryu Org. Lett, 2015, 17, 5 pp. 1292 - 1295 DOI: 10.1021/acs.orglett.5b00282
β- or γ-Site-selective C–H alkylation of aliphatic nitriles has been achieved using a decatungstate salt as the photocatalyst. The observed site selectivity was justified by a radical polar effect in transition states for hydrogen abstraction.