Palladium-Catalyzed Intermolecular Cyclocarbonylation of 2-Iodoanilines with the Michael Acceptor, Diethyl Ethoxycarbonylbutendienoate

Palladium-catalyzed intermolecular cyclocarbonylation of 2-iodoanilines with diethyl ethoxycarbonylbutendienoate produces 2,3,3-triethoxycarbonyl-2,3-dihydro-4­(1<i>H</i>)-quinolinone derivatives in moderate to good yields. This protocol involves Michael addition and subsequent carbonylation

Synthesis of Pyrido[2,1‑<i>b</i>]quinazolin-11-ones and Dipyrido[1,2-a:2′,3′‑<i>d</i>]pyrimidin-5-ones by Pd/DIBPP-Catalyzed Dearomatizing Carbonylation

N-Fused heterocycles can be easily synthesized by palladium-catalyzed dearomatizing carbonylation using 1,3-bis­(diisobutylphosphino)­propane (DIBPP) as the ligand. Pyrido­[2,1-<i>b</i>]­quinazolin-11-ones were obtained from <i>N</i>-(2-bromophenyl)­pyridine-2-amines in up to quantitative yield and dipyrido­[1,2-a:2′,3′-<i>d</i>]­pyrimidin-5-ones from 3-bromo-<i>N</i>-(pyridine-2-yl)­pyridine-2-amines in up to 84% yield. The cyclocarbonylation can be also realized without isolation of compound <b>1</b> and additional palladium catalyst

Synthesis of Indolizine Derivatives by Pd-Catalyzed Oxidative Carbonylation

An efficient synthesis of indolizine derivatives by palladium-catalyzed oxidative carbonylation of propargylic pyridines has been developed. The reaction can be conducted at room temperature and under 3 bar of CO in the presence of Pd₂(dba)₃ or Pd/C. The catalyst Pd/C could be easily removed from the reaction and recycled

Ligand- and Additive-Controlled Pd-Catalyzed Aminocarbonylation of Alkynes with Aminophenols: Highly Chemo- and Regioselective Synthesis of α,β-Unsaturated Amides

This work describes the chemo- and regioselective direct aminocarbonylation of alkynes and aminophenols to form hydroxy-substituted α,β-unsaturated amides in good to excellent yields. The latter are valuable compounds in pharmaceuticals and natural products. By a simple choice of different ligands and additives, branched or linear isomers could be selectively formed in excellent regioselectivity. Using a combination of boronic acid and 5-chlorosalicylic acid (“BCSA”) as the additives, linear amides were obtained in high yields and selectivities using 1,2-bis­(di-<i>tert</i>-butylphosphinomethyl)­benzene (DTBPMB) as the ligand. On the other hand, branched amides could be approached by introducing 1,3-bis­(diphenylphosphino)­propane as the ligand and <i>p</i>-TsOH·H₂O as the additive. In addition to the hydroxyl group, other functional substituents, such as carboxyl and vinyl groups, could also be tolerated using this method. As an application of this strategy, the natural product avenanthramide A could be synthesized directly in 84% yield and in 99% regioselectivity via the carbonylation of 2-amino-5-hydroxybenzoic acid and 4-ethynylphenol. Further studies show that the ligands and the additives are keys to good yields and selectivities

PdI₂‑Catalyzed Regioselective Cyclocarbonylation of 2‑Allyl Phenols to Dihydrocoumarins

A simple, efficient, and regioselective synthesis of 3-methyl-3,4-dihydro­coumarins is reported. The reaction of 2-allyl phenols with synthesis gas was catalyzed by PdI₂, and 1,3,5,7-tetra­methyl-6-phenyl-2,4,8-trioxa-6-phos­pha­adaman­tane (<b>L1</b>) and 1,3,5,7-tetra­methyl-6-tetra­decyl-2,4,8-trioxa-6-phospha­adaman­tane (<b>L2</b>) were effective as ligands, affording good product selectivity in all cases

Regioselective Alkoxycarbonylation of Allyl Phenyl Ethers Catalyzed by Pd/dppb Under Syngas Conditions

A simple and regioselective synthesis of phenoxy esters and phenylthio esters is reported. The products are obtained by selective alkoxycarbonylation catalyzed by Pd₂(dba)₃, 1,4-bis­(diphenylphisphino)­butane (dppb), and syngas (CO/H₂) in chloroform/alcohol. This methodology affords bifunctional products in good yield with excellent n-selectivity and without the need to use additives

Synthesis of Coumarins via Pd-Catalyzed Oxidative Cyclocarbonylation of 2‑Vinylphenols

Palladium-catalyzed oxidative cyclocarbonylation of 2-vinylphenols constitutes a simple, direct method for the synthesis of coumarins. The reaction conditions, employing low pressures of CO, and air or 1,4- benzoquinone as the oxidant, are attractive in terms of environmental considerations and operational simplicity. Coumarins with a variety of functional groups were prepared in yields up to 85%

Highly Ligand-Controlled Regioselective Pd-Catalyzed Aminocarbonylation of Styrenes with Aminophenols

Achieving chemo- and regioselectivity simultaneously is challenging in organic synthesis. Transition metal-catalyzed reactions are effective in addressing this problem by the diverse ligand effect on the catalyst center. Ligand-controlled regioselective Pd-catalyzed carbonylation of styrenes with aminophenols was realized, chemoselectively affording amides. Using a combination of boronic acid and 5-chlorosalicylic acid as the additives, linear amides were obtained in high yields and selectivity using tris­(4-methoxyphenyl)­phosphine (<b>L3</b>) in acetonitrile, while branched amides were obtained in high yields and selectivity in butanone by changing the ligand to 1,3,5,7-tetramethyl-2,4,8-trioxa-6-phenyl-6-phosphaadamantane (<b>L5</b>). Further studies show that the nature of the ligand is key to the regioselectivity. Cone angle and Tolman electronic parameter (TEP) have been correlated to the reactivity and regioselectivity. Studies on the acid additives show that different acids act as the proton source and the corresponding counterion can help enhance the reactivity and selectivity

Copper-Catalyzed Cascade Substitution/Cyclization of <i>N</i>‑Isocyanates: A Synthesis of 1‑Aminobenzimidazolones

A copper-catalyzed cascade reaction of in situ generated nitrogen-substituted isocyanates (<i>N-</i>isocyanates) and 2-iodoanilines has been developed. The cascade relies on the base-catalyzed substitution of masked <i>N</i>-isocyanates, followed by Cu­(I)-catalyzed coupling to afford a variety of 1-aminobenzimidazolones in moderate to excellent yields. This is the first example of a transition-metal-catalyzed cascade reaction involving <i>N</i>-isocyanate intermediates

Pd-Catalyzed Regioselective Alkoxycarbonylation of 1‑Alkenes Using a Lewis Acid [SnCl₂ or Ti(O^<i>i</i>Pr)₄] and a Phosphine

The phosphine ligand mediated palladium catalyzed alkoxycarbonylation of alkenes was investigated with the objective of attaining good linear selectivity for the ester. The effect of various parameters such as solvents, additives, palladium precursors, CO pressures, and alkenes of various structural complexities were examined. The results revealed the importance of using a Lewis acid such as SnCl₂ or Ti­(O^<i>i</i>Pr)₄ in combination with a monodentate ligand such CYTOP 292 or P­(<i>p</i>-anisyl)₃ to enhance the regioselectivity for the linear isomers in the range of 70–96%