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Palladium-catalyzed the Coupling Reactions Involving Dialkyl H-phosphonate or Terminal Alkynes

Author: XuKai
Tutor: WuYangJie
School: Zhengzhou University
Course: Organic Chemistry
Keywords: palladacycle-catalyzed phosphonation aryl chloride terminal alkynes diarylacetylenes Sonogashira coupling in water
CLC: O643.32
Type: PhD thesis
Year: 2013
Downloads: 79
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Abstract

Cyclopalladated ferrocenylimine (Palladacycle I or II) catalyzed the cross-coupling of aryl halides with diisopropyl H-phosphonate efficiently both in organic solvents and neat water. With the base of K2CO3as the promoter, the arylmethylation could be carried out under metal-free conditions. In addition, palladacycle I catalyzed the Sonogashira cross-coupling of aryl chlorides with terminal alkynes and applied to the one-pot synthesis of symmetrical diarylacetylenes starting from aryl chlorides and2-methyl-3-butyn-2-ol both in acetonitrile and neat water. It should be noted that palladacycle I could be applied to the one-pot synthesis of unsymmetrical diarylacetylenes starting from two different aryl chlorides and2-methyI-3-butyn-2-ol in acetonitrile.1. Synthesis of aryl and arylmethyl phosphonates by cross-coupling of aryl or arylmethyl halides (X=I, Br and Cl) with diisopropyl H-phosphonate An efficient and generally applicable protocol for the palladacycle-catalyzed arylation or K2CO3-promoted arlmynethylation of diisopropyl H-phosphonate was developed. The remarkable features of the palladacycle-catalyzed arylation include wide substrate scope (aryl iodides, bromides and chlorides), significant shortening of the reaction time (2or3h), and low catalyst loading of1mol%. It should be noted that with the base of K2CO3as the promoter, the arylmethylation could be carried out under metal-free conditions.(Scheme1).2. Palladacycle-catalyzed phosphonation of aryl halides in neat waterAn efficient and generally applicable protocol for the palladacycle-catalyzed arylation of diisopropyl H-phosphonate in water was developed. The remarkable features of this C-P bond forming reaction include wide substrate scope including the inactive electron-rich and electron-neutral aryl chlorides, the weak inorganic base KF instead of strong bases such as KO’Bu or NaO’Bu for the activation of C-Cl bond, and the addtion of isopropanol to avoid the decomposition of diisopropyl H-phosphonate (Scheme2).3. Palladacycle-catalyzed the one-pot synthesis of symmetrical and unsymmetrical diarylacetylenes starting from aryl chlorides via Sonogashira couplingAn efficient and general synthetic method has been developed for the preparation of symmetrical and unsymmetrical diarylacetylenes from the reaction of aryl chlorides with2-methyl-3-butyn-2-ol catalyzed by palladacycle/X-Phos under mild reaction conditions. It is worthy to note that unsymmetrical diarylated acetylenes could also be obtained by one-pot reaction of two different aryl chlorides with2-methyl-3-butyn-2-ol. The catalytic procedure proceeded through a novel one-pot palladium-catalyzed, twice Sonogashira coupling of inactivated aryl chlorides without use of copper(I) as co-catalyst (Scheme3). 4. Palladacycle-catalyzed the one-pot synthesis of symmetrical diarylacetylenes starting from aryl chlorides via Sonogashira coupling in neat water One-pot synthesis of symmetrical diarylacetylenes in neat water was successfully catalyzed by palladacycle/X-Phos in the presence of SDS starting from commercially available aryl chlorides and2-methyl-3-butyn-2-ol (Scheme4).

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