Synthesis of Long-Chain Alkanoyl Benzenes by an Aluminum(III) Chloride-Catalyzed Destannylative Acylation Reaction

Abstract

This paper describes the facile synthesis of haloaryl compounds with long-chain alkanoyl substituents by the destannylative acylation of haloaryls bearing tri-n-butyltin (Bu 3 Sn) substituents. The method allows the synthesis of many important synthons for novel functional materials in a highly efficient manner. The halo-tri-n-butyltin benzenes are obtained by the lithium−halogen exchange of commercially available bis-haloarenes and the subsequent reaction with Bu 3 SnCl. Under typical Friedel−Crafts conditions, i.e., the presence of an acid chloride and AlCl 3 , the haloaryls are acylated through destannylation. The reactions proceed fast (<5 min) at low temperatures and thus are compatible with aromatic halogen substituents. Furthermore, the method is applicable to para-, meta-, and ortho-substitution and larger systems, as demonstrated for biphenyls. The generated tin byproducts were efficiently removed by trapping with silica/KF filtration, and most long-chain haloaryls were obtained chromatography-free. Molecular structures of several products were determined by X-ray single-crystal diffraction, and the crystal packing was investigated by mapping Hirshfeld surfaces onto individual molecules. A feasible reaction mechanism for the destannylative acylation reaction is proposed and supported through density functional theory (DFT) calculations. DFT results in combination with NMR-scale control experiments unambiguously demonstrate the importance of the tin substituent as a leaving group, which enables the acylation.

Cu(I) Mediated Azidation of Halobenzenes, and Cu Catalysed Selective Azide Reduction to Corresponding Amines

“…In principle, two synthetic routes are applicable for the synthesis of multifunctional amines 5 (Scheme 1) We have previously employed route 2 for preparation of a para-derivative, [5] starting from haloalkanoyl benzenes. [18] In the current work we have further investigated this route, and an alternative route 1, which involves isolation of the new versatile amineazides type 7. Installation of the aliphatic azide and generation of the aryl amine can be achieved simultaneously.…”

“…The initial steps are routine (Scheme 2). The long-chain bromoalkanoyl halobenzenes 1 [18] are converted to the corresponding aliphatic azides 2 and a click reaction with propargylpyrazole (PrPy) affords the pyrazole-triazole (PyT) moieties in good to excellent yields. Amination in EtOH/water.…”

Copper(I) Chloride Mediated Amination of Halobenzenes via Azides: Scope, Mechanistic Aspects, and C–C Cleavage Reactions

“…In order to understand the alkyl cleavage better, we conducted further controls. We synthesized an analogous aryl bromo precursor with an (unfunctionalized) undecanoyl chain (1b, Scheme 1) by a tin-mediated acylation 32 �this derivative simplifies the transformation as no halide−azide exchange occurs simultaneously at the aliphatic Br-position. When 1b was subjected to the same reaction conditions, alkyl cleavage occurred as well.…”

“…The known halobenzene precursors bearing alkanoyl chains, 1aa, 1ab, 1ac, 1ad, and 1c-1e, were prepared as previously reported. 32 The other known halobenzenes, 1f, 1fb, and 1g−1m, were obtained commercially.…”

“…We have investigated the reactions for functionalized halobenzenes bearing long alkyl chains 32 and conventional substrates (Figure 1). The protocol allows the one-pot synthesis of anilines from the corresponding halobenzenes and is applicable for substrates with electron-withdrawing groups.…”