Synthesis of N-(Anthracen-9-ylmethyl)-N-methyl-2-(phenylsulfonyl)ethanamine via Microwave Green Synthesis Method: X-ray Characterization, DFT and Hirshfeld Analysis

N-(Anthracen-9-ylmethyl)-N-methyl-2-(phenylsulfonyl)ethanamine 3 has been synthesized via the aza-Michael addition approach by reaction of the corresponding amine with the vinyl sulfone derivative under microwave conditions. The structure of the aza-Michael product 3 is elucidated by X-ray crystallography. The study of molecular packing by employing the Hirshfeld analysis indicates that the percentages of O…H, C…H and H…H contacts are 16.8%, 34.1% and 48.6%, respectively, where the O...H hydrogen bonds have the characteristics of short and strong contacts while the C...H contacts are considered weak. Density functional theory (DFT) investigations show that the aza-Michael product 3 is polar with a net dipole moment of 5.2315 debye.

Multi-step degradation method for β-O-4 linkages in lignins: α-TSA method. Part 1: Reaction of non-phenolic dimeric β-O-4 model compound

The α-TSA method has been developed for the cleavage of β-O-4 linkages in lignin. It consists of three steps: (1) thioetherification at α-position of β-O-4 substructures, (2) sulfonylation, and (3) mild alkali treatment of the α-sulfone derivative. The method was tested on a nonphenolic dimeric β-O-4 lignin model compound, namely on 4-benzyloxy-3-methoxyphenylglycerol-β-guaiacyl ether. It demonstrated that the mild alkali degradation of the α-sulfone derivative proceeds efficiently, i.e., the electron-withdrawing sulfone group at α-position contributes to the cleavage of the β-O-4 linkage in the same mechanism as that in the γ-TTSA method.

Use of (S)-trans-γ-Monocyclofarnesol as a Useful Chiral Building Block for the Stereoselective Synthesis of Diterpenic Natural Products

A comprehensive study of the exploitation of ( S)- trans-γ-monocyclofarnesol as a useful chiral building block for the stereoselective synthesis of natural diterpene derivatives is here described. The farnesol derivative (+)-1 was used as starting material in the preparation of the diterpenes ( S)-dehydroambliol-A and ( S)-trixagol, as well as for the syntheses of the dinorditerpene ( S)-dinortrixagone and of the guanidine-interrupted terpenoid ( S)-dotofide. Key steps of the presented syntheses were the cross-coupling between an allyl acetate and a Grignard reagent, the Wittig reaction, the selective preparation of a diacylguanidine derivative and the alkylation of a sulfone derivative, followed by the reductive removal of the same functional group. It is worth noting that the natural products (+)-8, (+)-12 and (+)-15 were prepared stereoselectively for the first time, thus allowing the unambiguous assignment of their absolute configuration.

Substituent effects on the structure of hexacoordinate carbon bearing two thioxanthene ligands

In order to elucidate the electronic nature of our recently reported first hexacoordinated carbon (12-C-6), density functional theory (DFT) calculations of sulfide precursor, sulfone derivative, and S+-F derivative were carried out and compared with those of the reported S+-Me hexacoordinated carbon. Computations on the hexacoordinated carbon, indicating that four attractive C–O interactions with the central hexacoordinate carbon atom exist, also revealed that the interactions consist of two different types of three-center four-electron bonds, which can be regarded as electron donation by the lone pairs of the oxygen atoms to the empty low-lying π*-orbitals of the allene. The optimized structures of the sulfide, sulfone, S+-F, and the original S+-Me suggested that the introduction of electron-withdrawing groups at the sulfur atoms would make the C–O attractive interactions stronger by a larger contribution of the carbon dication resonance structure. Thus, allene compounds (sulfide, sulfone, sulfonium) with two different thioxanthene ligands (one with 1,8-dimethoxy groups as in the S+-Me compound and the other with 1,8-diphenoxy groups) were synthesized to confirm the predicted substituent effects on the C(central)–O interactions. Electron-withdrawing substituents at the sulfur atoms were found to give rise to strong C(central)–O attractive interactions; the average values of the four C–O distances were smaller as the electron-withdrawing ability of the sulfur atoms rose. Additionally, C(central)···OMe distances were shorter than the corresponding C(central)···OPh distances, reflecting the higher electron-donating ability of the oxygen atoms at these 1,8-positions of the thioxanthene skeleton.