ChemDigest

A rhodium‐catalyzed reductive esterification of carboxylic acids with carbonyl compounds was developed. This protocol fits a variety of carboxylic acids and aldehydes, opening the short way from industrial bulk compounds to valuable esters.

Carbon monoxide used to have a limited number of applications in organic chemistry, but it gradually increases its role as a mild and selective reducing agent. It can be applied for the carbon–heteroatom single bond formation via the reductive addition of hydrogen‐containing nucleophiles to carbonyl compounds. In this paper, rhodium‐catalyzed reductive esterification is described, and a comparative study of the rhodium and ruthenium catalysis in the reductive addition reactions is provided. Rhodium performs better on highly nucleophilic substrates and ruthenium is better for compounds with less nucleophilicity.

Here, we are reporting a simple synthetic strategy for the synthesis of thiacyclophanes by using the Grignard reaction and ring‐closing metathesis as key steps. The structures are confirmed by single‐crystal XRD diffraction studies and compared with computationally optimized structures.

We report a useful synthetic strategy to assemble constrained [3.n] thiacyclophanes using Grignard reaction and Ti(Oi Pr)₄ assisted ring‐closing metathesis (RCM). This method is viable to access para, metapara, and meta isomers of thiacyclophanes. The structures of thiacyclophanes were confirmed unambiguously by single‐crystal X‐ray diffraction studies and compared with computationally optimized structures. It is implied that out of four methods (ab initio and DFT), MP2/6‐31G (d,p) is reasonably a better method for predicting structural parameters for this class of thiacyclophanes.

The total synthesis of a novel antitumor cyclic depsipeptide FE399 was achieved mainly through the MNBA‐mediated macrolactamization. A combination of MNBA and a catalytic amount of DMAPO in the presence of triethylamine as coupling agents was found to be effective for the synthesis of the macrolactam core of FE399.

An efficient and practical method for the synthesis of (9R ,14R ,17R )‐FE399, a novel antitumor bicyclic depsipeptide, was developed. A 2‐methyl‐6‐nitrobenzoic anhydride (MNBA)‐mediated dehydration condensation reaction was effectively employed for the formation of the 16‐membered macrocyclic depsipeptide moiety of FE399. FE399 was found to exist as an inseparable equilibrium mixture of conformational isomers; the mixture was quantitatively transformed into the corresponding S‐benzyl product and isolated as a single isomer. Thus, we could confirm that the molecular structure of FE399 obtained by this method is identical to that of the natural product.

The first metal‐catalyzed C3‐nucleophilic (4+3) cyclization of 2‐indolylmethanols with stable ortho‐quinone methides has been established, which was used to construct indole‐based seven‐membered heterocycles in high yields (up to 98 %) with regiospecificity.

The first metal‐catalyzed C3‐nucleophilic (4+3) cyclization of 2‐indolylmethanols with stable ortho‐quinone methides has been established, which constructed indole‐based seven‐membered heterocycles in high yields (70 %‐98 %) with regiospecificity. This reaction has tackled the challenges in exploring the C3‐nucleophilicity of 2‐indolylmethanols, which will contribute to the chemistry of 2‐indolylmethanols, especially to metal‐catalyzed cyclizations of 2‐indolylmethanols. In addition, this approach will provide a useful method for constructing indole‐based seven‐membered heterocycles with high efficiency and regioselectivity.

A Ag^I‐catalyzed [3+2] cycloaddition between diazomethyl sulfones and sulfonamides with arenediazonium tosylates provides regiospecific access to novel tetrazoles. The reaction products can be obtained in moderate to good yields.

The scope of silver nitrate‐catalyzed cycloaddition of arenediazonium salts has been expanded to include aryl‐ and alkylsulfonyl diazomethanes as well as the recently introduced diazomethyl sulfonamides. The reliance on these two classes of diazo compounds led to a new synthetic approach to the rare 2‐aryltetrazol‐5‐yl sulfones as well as to the synthesis of hitherto not described 2‐aryltetrazol‐5‐yl sulfonamides.