Palladium-catalyzed Exchange of Allylic Groups of Ethers and Esters with Active Hydrogen Compounds. II.

Abstract

The allylic compounds (I), R1–O–R (R=allylic groups, R1=Ph, Me, PhCH2, MeCO), react with active-hydrogen compounds such as phenols, alcohols, carboxylic acids, primary and secondary amines and active methylene compounds, to give allylic derivatives of the active-hydrogen compounds by an intermolecular exchange of the allylic groups of I with the atom to which the active hydrogens are bonded in the presence of palladium catalysts. Allyl and substituted-allyl ethers are more reactive than the corresponding carboxylates. In the reactions of methyl and benzyl ethers, it is necessary to add phenol to obtain the exchange products in fairly good yields. Bis(triphenylphosphine) palladium chloride plus sodium phenoxide, palladium acetate plus triphenylphosphine, and zerovalent palladium complexes such as tetrakis (triphenylphosphine) palladium and (maleic anhydride)bis(triphenylphosphine)palladium are effective catalysts.

Lewis Acid-Catalyzed Propargylic Etherification and Sulfanylation from Alcohols in MeNO2-H2O

“…In contrast, 2°alcohols such as cyclopentanol and cyclohexanol afforded 2ad and 2ae (entries 3 and 4). Surprisingly, both 1°and 2°alcohols are also nucleophilic toward propargyl cations in MeNO 2 -H 2 O. Alcohols bearing other aromatic substituents at the R 1 -position were examined with the 1°and 2°alcohols (entries [6][7][8][9][10][11][12][13][14][15][16][17]. Alcohol 1d, bearing the bulky aromatic substituent, 2,4,6-trimethylphenyl, also produced propargylic ether 2da in excellent yield (entry 12).…”

“…46) formed the reaction with other thiols such as 2-thienyl, naphthyl, p-chlorophenyl and cyclohexylthiol and obtained satisfactory results (entries 2-5, Table 4). A variety of propargyl alcohols bearing the substituents such as R 1 ϭ2-thienyl, 1-naphthyl and benzodioxol-5-yl produced some propargyl sulphides 8ba-8gc in moderate to high yields (entries [6][7][8][9][10][11]. Surprisingly, Lewis acid-catalyzed C-S bond formation with thiols generally proceeded without further addition of thiols to the alkynyl group, and the desired propargyl sulphides were obtained in good to high yields (entries 1-11).…”

“…However, substitution of hydroxyl group in an alcohol generally requires the prior activation of the hydroxyl group because of the poor leaving ability of this group. 5,6) An alcohol used as a precursor for carbocations is usually activated by transforming it to the corresponding acetate, [7][8][9][10][11][12][13][14][15][16][17] carbonate, 18,19) halide, 20) phosphonate. 21,22) Prior activation of an alcohol is also necessary if it has to be used as a nucleophile because of its low nucleophilicity.…”

ChemInform Abstract: Designer‐Surfactant‐Enabled Cross‐Couplings in Water at Room Temperature

“…28 These are unconventional partners in Pd-catalyzed couplings, where activation of the hydroxyl group in an allylic alcohol typically takes place in the form of an acetate, carbonate, sulfonate, or phosphate. 29 Nonetheless, under the influence of the hydrophobic effect, and in the presence of excess K 2 CO 3 and methyl formate, couplings result in amination predominantly at the least hindered, terminal site and give high E:Z ratios (eq 3). 28 DPEPhos ( 15 ) 30 was found to be the ligand of choice, while the more rigid analogue XantPhos ( 16 ) 31 led to only traces of allylic amines.…”

Palladium-Catalyzed Heck-Type Coupling of Allyl Esters: β-Hydride versus β-Acetoxy Elimination

“…The initial palladium(0) complex is regenerated at the end and initiates the next catalytic cycle. p-Allylmetal complexes are readily available from allyl acetates, 5 and a great variety of substrates can serve as nucleophiles which makes this reaction a strong competitor to Heck-type processes in the transition-metal-catalyzed coupling of allyl esters. The synthetic utility of the Tsuji-Trost reaction has been soundly demonstrated in organic synthesis.…”