Alkylation Tetrakis palladium

The ring closure to form butenolides by palladium(O) catalysis can be combined with C,C bond linking, as shown by Ma and co-workers. If using tetrakis (triphenyl -phosphane)palladium(O), the products 272 are obtained from 268 (R1 = alkyl, R2 = H) and vinyl iodides or aryl bromides and iodides R3X [304]. The authors assume that... 

Substitution reactions of allylic nitro compounds often lead to rearranged products, as in palladium(0)-catalysed aminations and alkylations. Thus treatment of the nitro ester 419 with piperidine in the presence of tetrakis(triphenylphosphine)palladium yields a mixture of the unrearranged and rearranged amines 420 (R = piperidin-l-yl) and 421... 

Cyclopentanone synthesis. The palladium reagent (I), as well as tetrakis(tri-phenylphosphine)palladium, promotes a 1,3-alkyl shift from oxygen to carbon with no allylic inversion. Two typical examples are formulated.1... 

The oxidative addition is quite general with alkyl, allyl, benzyl, vinyl, and aryl halides as well as with acyl halides to afford the palladium (II) complex VII. The frans-bis( triphenylphosphine )alkylpalladium halides can also be carbonylated in an insertion reaction to give the corresponding acyl complexes, the stereochemistry of which (17, 18) proceeds with retention of configuration at the carbon bonded to palladium. The acyl complex also can be formed from the addition of the corresponding acid halide to tetrakis (triphenylphosphine) palladium (0). 

Stereoselective allylic alkylations have been carried out with the aid of palladium catalysts. The 17-(Z)-ethylidene groups of steroids (obtained from the ketones by Wittig olefination) form n-allyl palladium complexes in the presence of copper(n) salts (B.M. Trost, 1974, 1976). Their alkylation with dimethyl malonate anions in the presence of 1,2-ethane-diylbis[diphenylphosphine] (— diphos) gives a reaction exclusively at the side chain and only the (20S) products. If one starts with the endocyclic 16,17 double bond and replaces an (S)-20-acetoxy group by using tetrakis(triphenylphospbine)palladium,the substitution occurs with complete retention of configuration, resulting from two complete inversions (B.M. Trost, 1976). 

A palladium-catalyzed reaction has been reported to C-6 alkylate 6-bromoimidazo[4,5-h]pyridine (109) <87EUP290153>. In this reaction, 2-methoxy-6-bromo-8-methylquinoline (110) was treated with butyllithium to give the 6-lithiated derivative (111). To this compound (111) was added zinc chloride, followed by 6-bromoimidazo[4,5-/>]pyridine (109) and tetrakis(triphenylphosphine)palladium(0)... 

In 1980 Trost and Keinan reported on allylic alkylations of tin enolates such as 33 catalyzed by tetrakis(triphenylphosphine)palladium (equation 12). The stannyl ethers led to a rapid and clean monoaUcylation with high regioselectivity. Thereby, alkylation generally occurred at the less substituted end of the allyl moiety with formation... 

Enantioselective Allylic Alkylation. Reaction of l-(a-acet-oxyethyl)cyclopentene with the sodium salt of dimethyl mal-onate in refluxing 1,2-dimethoxyethane, when performed in the presence of tetrakis(triphenylphosphine)palladium and (R,S)-CAMPHOS catalyst, afforded the corresponding ct-alkylated malonic ester in 99% chemical yield (37% ee)(eq 3). Comparable results were obtained when this reaction was performed in THF solution by using Pd(PPh3)4-(S,S)-(+)-DIOP as catalyst. ... 

Substitution of chlorine atoms in 2.4-dichloroquinazoline with alkyl groups is readily effected under the influence of palladium catalysis with trialkylaluminum acting as donor of the alkyl group. Selectivity for position 4 in 2,4-dichloroquinazoline can be achieved with trimethyl- and triisobutylaluminum under the influence of tetrakis(triphenylphosphane)palladium(0) as catalyst. In the presence of another molar equivalent or more of trialkylaluminum, products 14 which carry the same or a different alkyl group in the 2-position are formed. ... 

This methodology has also been applied to the conversion of alkyl esters into vinyl ethers with high stereoselectivity favoring the (Z)-isomer (Scheme 30). While standard Li/amine reduction conditions were not applicable, the enol phosphates could be reduced using triethylaluminum and tetrakis(tri-phenylphosphine)palladium. 

Kosugi, M., Shimizu, Y., Migita, T. Alkylation, arylation, and vinylation of acyl chlorides by means of organotin compounds in the presence of catalytic amounts of tetrakis(triphenylphosphine)palladium °. Chem. Lett. 1977, 1423-1424. 

Enol ethers of alkyl cyclopropyl ketones are alkylated or carboxylated under the correct conditions. Methyl ann, c ,cw-2,9,9-trimethyl-5-trifluoromethylsulfonyloxytricyclo[5.3.0.0 " ]dec-5-ene-4-carboxylate on treatment with palladium(II) acetate in methanol containing triethylamine under a carbon monoxide atmosphere resulted in diester formation giving dimethyl fln ,c .5,cw-2,9,9-trimethyltricyclo[5.3.0.0 ]dec-5-ene-4,5-dicarboxylate in excellent yield (93%). The same substrate was converted to methyl anr/,cw,d. -5-formyl-2,9,9-trimethyltricyclo[5.3.0.0 ]dec-5-ene-4-carboxylate in 88% yield on carbonylation in the presence of tetrakis(triphenylphosphane)palladium, tributyltin hydride, and lithium chloride. ... 

Chiral allylic cyclic carbonates such as 551 or 552 undergo excellent regioselective alkylation reactions with soft nucleophiles in the presence of palladium(O) in refluxing THF to provide ( )-allylic alcohols. The reaction of 4-0-benzyl-2,3-isopropylidene-L-threose (167) with the appropriate ylid, followed by deprotection of the isopropylidene ring with acidic resin and cyclic carbonate formation, provides a good overall yield of either 551 or 552. Ring opening with diethyl malonate in the presence of tetrakis(triphenylphosphine)palladium(0) provides in excellent yield the allylic alcohols 553 or 554, where the diastereoselectivity exceeds 99%. This reaction represents an efficient method of 1,3-chirality transfer [180] (Scheme 122). 

Oxidative addition of palladium(O) species into unsaturated halides or triflates provides a popular method for the formation of the a-bound organopalladium(II) species. It is important to use an unsaturated (e.g. aryl or alkenyl) halide or tri-flate, as (3-hydride elimination of alkyl palladium species can take place readily. Oxidative addition of palladium(0) into alkenyl halides (or triflates) occurs stere-ospecifically with retention of configuration. The palladium is typically derived from tetrakis(triphenylphosphine)palladium(0), [Pd(PPh3)4], or tris(dibenzylidene-acetone)dipalladium(O), [Pd2(dba)3], or by in situ reduction of a palladium(II) species such as [Pd(OAc)2] or pd(PPh3)2Cl2]. 

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