Novel tetrahydropyrimidinium / palladium system as a convenient catalyst: Suzuki coupling reactions of aryl chlorides

2007 ARKIVOC  
Four bis(3,4,5,6-tetrahydropyrimidinium) chlorides (2a-d) have been prepared and characterized by conventional spectroscopic methods and elemental analyses. A highly effective, easy to handle and environmentally benign process for palladium mediated Suzuki cross-coupling was developed. The in situ prepared three-component system Pd(OAc) 2 / bis(3,4,5,6tetrahydropyrimidinium) chlorides (2a-d) and K 2 CO 3 catalyses quantitatively the Suzuki crosscoupling of deactivated aryl chlorides. of this
more » ... lorides. of this reaction is broad and includes aryl chlorides that are activated or deactivated. Third, all ligands led to good conversions at low catalyst concentration (1.5 mmol %). The procedure is simple and efficient towards various aryl halides and does not require induction periods. Experimental Section General Procedures. All reactions for the preparation of 1-methyl-3,4,5,6-tetrahydropyrimidine (1) and bis(1-methyl-3,4,5,6-tetrahydropyrimidine) chlorides 27 (2a-d) were carried out under argon using standard Schlenk-type flasks. Test reactions for the catalytic activity of catalysts in the Suzuki cross-coupling reactions were carried out in air. All reagents were purchased from the Aldrich Chemical Co. The solvents, were distilled prior to use: Et 2 O over Na, DMF over BaO, EtOH over Mg. All 1 H and 13 C-NMR were registered in DMSO-d 6 . 1 H NMR and 13 C NMR spectra were recorded using a Bruker AC300P FT spectrometer operating at 300.13 MHz ( 1 H), 75.47 MHz ( 13 C). Chemical shifts (δ) are given in ppm relative to TMS and coupling constants (J) in Hz. Infrared spectra were recorded as KBr pellets in the range 400-4000 cm -1 on a ATI UNICAM 1000 spectrometer. Melting points were measured in open capillary tubes with an Electrothermal-9200 melting point apparatus and are uncorrected. Elemental analyses were performed by TUBITAK (Ankara, Turkey) Microlab. General Papers ARKIVOC 2007 (xiii) 71-78
doi:10.3998/ark.5550190.0008.d10 fatcat:sct4pajo7jcerbkwva3w5m5v2m