Acac

Catalysts VO(acac)2 Mo(CO)e Ti(OiPr)4 Oxidant tBuOOH PhC(CH3)200H... 

Donor strengths, taken from ref. 207b, based upon the solvent effect on the symmetric stretching frequency of the soft Lewis acid HgBr2. Gutmann s donor number taken from ref 207b, based upon AHr for the process of coordination of an isolated solvent molecule to the moderately hard SbCL molecule in dichioroethane. ° Bulk donor number calculated as described in ref 209 from the solvent effect on the adsorption spectrum of VO(acac)2. Taken from ref 58, based on the NMR chemical shift of triethylphosphine oxide in the respective pure solvent. Taken from ref 61, based on the solvatochromic shift of a pyridinium-A-phenoxide betaine dye. 

The phenylation of styrene with phenyl Grignard reagents as a hard carbon nucleophile proceeds in 75% yield in the presence of PdCl2, LiCl, and K2CO3 at room temperature to give stilbene (207). Selection of the solvent is crucial and the best results are obtained in MeCN. The reaction can be made catalytic by the use of CuCl2[197]. Methyllithium reacts with styrene in the presence of Pd(acac)2 or Pd(OAc)2 to give /3-methylstyrene (208) in 90% yield[198]. 

Efficient homocoupling of the aryi iodonium salt 827 using Zn is catalyzed by Pd(acac)2[708], Homocoupling of the aryisuifonyl chloride 828 as a pseudohalide takes place in the presence of 2 equiv. of Ti tctraisopropoxide[7Q9]. 

Chemoselectivity in the cycloaddition of 2-methylenecycloheptenone (174) changes on addition of In(acac)3. The allylic carbonate 175 reacts with the ketone 174 in the presence of In(acac)3 to give the methylenetetrahydrofuran 176, and the methylenecyclopentane 177 is obtained in its absence[l 13], The cycloaddition of ynones to produce the methylenetetrahydrofuran proceeds smoothly only in the presence of In(acac)3 (10 mol%)[114]. 

The preparative method for the Pd(0) catalyst active in these regioselective eliminations under mild conditions is crucial. The very active catalyst is prepared by mixing equimolar amounts of Pd(OAc) or Pd(acac)2 and pure n-... 

The reaction of isoprene with MeOH catalyzed by Pd(acac)2 and Ph3P is not regioselective, giving a mixture of isomers[37]. However, l-methoxy-2,6-dimethyl-2,7-octadiene (35), the head-to-tail dimer, was obtained in 80% yield, accompanied by the tail-to-tail dimer (15%) using 7r-allylpalladium chloride and BU3P. On heating, 35 was converted into 2.6-dimethyl-1,3,7-octatriene (36) by an elimination reaction[38]. 

The reaction of isoprcnc with Et NH in the presence of triethylammonium iodide (10 mol%) gives the 1 1 adducts 51 and 52 with high selectivity(53]. The reaction of isoprene with ammonia or diethylamine affords the tail-to-tail dimer 53 when Pdfacac) and (BuO)jP are used as the catalyst. The head-to-head dimer 54 is obtained with Pd(acac)2, BF,. and tricyclohexylphosphine(54]. 

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