Palladium tert-butyl

The method is basically an application of the Wacker oxidation except that the catalyst used is palladium acetate ( Pd(AcO)2 or Pd(02CCH3)2). the solvent is acetic acid or tert-butyl alcohol and the oxygen source is the previously suggested hydrogen peroxide (H202)[17]. 

A solution of 1.7 g of 2-hydroxymethyl-3-benzyloxy-(1-hydroxy-2-tert-butyl-aminoethyl)py-ridine in 30 ml of methanol containing 1.2 ml of water is shaken with 700 mg of 5% palladium-onatmospheric pressure. In 17 minutes the theoretical amount of hydrogen has been consumed and the catalyst is filtered. Concentration of the filtrate under reduced pressure provides 1.4 g of the crude product as an oil. Ethanol (5 ml) Is added to the residual oil followed by 6 ml of 1.75N ethanolic hydrogen chloride solution and, finally, by 5 ml of Isopropyl ether. The precipitated product is filtered and washed with isopropyl ether containing 20% ethanol, 1.35 g, melting point 182 (dec.). 

Enantioselective allylations of a-nitro ketones and a-nitro esters with allyl acetates are carried out in the presence of 2 equiv of alkali metal fluorides (KF, RbF, CsF) and 1 mol% palladium catalysts prepared in situ from Pd2(dba)3-CHC13 and chiral phosphine ligands. Moderate enantio-selectivity (ca 50% ee) is reported for allylation of cx-nitroketones (Eq. 5.60). The highest selectivity (80% ee) is observed for allylation of the reaction of tert-butyl ester (Eq. 5.61).93... 

A mild and efficient a-heteroarylation of simple esters and amides via nucleophilic aromatic substitution has been described <06OL1447>. Treatment of 2-chloro-benzo[//Jthiazole 99 with tert-butyl propionate in the presence of NaHMDS under nitrogen furnishes tert-butyl 2-(benzo[c(jthiazol-2-yl)propanoate 100. When the same reaction is preformed initially under nitrogen and then exposed to air, the hydroxylation product 101 is obtained. This method offers two desirable features that are either complementary or improvements to the palladium-catalyzed a-arylation reactions. First, heteroaryl chlorides... 

The same authors [38] further refined these catalysts by developing very bulky cyclophane diimine palladium(II) catalysts (Fig. 5), which show greater activity and stability than their acyclic analogs. The incorporation levels of acrylates (methyl and tert-butyl acrylate were exemplified) are unusually high (up to around 25... 

The intramolecular arylation of sp3 C-H bonds is observed in the reaction of l-/ r/-butyl-2-iodobenzene under palladium catalysis (Equation (71)) 94 94a 94b The oxidative addition of Arl to Pd(0) gives an ArPdl species, which undergoes the electrophilic substitution at the tert-butyl group to afford the palladacycle. To this palladacycle, another molecule of Arl oxidatively adds, giving the Pd(iv) complex. 

A new type of asymmetric hydrosilylation which produces axially chiral allenylsilanes has been reported by use of a palladium catalyst coordinated with the bisPPFOMe ligand 51b.64 The hydrosilylation of l-buten-3-ynes substituted with bulky groups such as tert-butyl at the acetylene terminus took place in a 1,4-fashion to give allenyl(trichloro)-silanes with high selectivity. The highest enantioselectivity (90% ee) was observed in the reaction of 5,5-dimethyl-T hexen-3-yne with trichlorosilane catalyzed by the bisPPFOMe-palladium complex (Scheme 13). 

Common protectors of hydroxyls are benzyl and 2-bromobenzyl for Boc chemistry and tert-butyl for Fmoc chemistry. Trityl provides a third level of selectivity for both chemistries because it can be removed by mild acid (1% CF3C02H in CH2C12), which does not affect tert-butyl based protectors. O-Allyl is not removable by palladium-catalyzed allyl transfer, so it is not appropriate. Protection by acyl such as benzyloxycarbonyl is possible, but 0 -acyl protectors can be problematic because of their tendency to shift to adjacent amino groups (see Section 6.6) and... 

A convenient direct route has recently been described for obtaining regioregular polyalkylthiophenes using a tandem iridium-catalyzed borylation to produce the monomer, and a palladium-mediated coupling to produce the polymer [68]. The treatment of substituted thiophenes with B2pin2 in the presence of [lrCl2(COD)]2/ 4,4 -di-tert-butyl-2,2 -bipyridine (DTBPY) provided the expected monomer in 97% yield (Scheme 7.35). 

PALLADIUM-CATALYZED COUPLING OF VINYL TRIFLATES WITH ORGANOSTANNANES 4-tert-BUTYL-l-VINYLCYCLOHEXENE and l-(4-tert-BUTYLCYCLOHEXEN-l-YL)-2-PROPEN-l-ONE... 

Dihydro-2H-pyran 2H-Pyran, 3,4-dihydro- (8,9) (110-87-2) tert-Butyllithium Lithium, tert-butyl- (8) Lithium, (1,1-dimethylethyl)- (9) (594-19-4) Palladium(ll) chloride bisacetonitrile Aldrich Bis(acetonitrile)dichloropalladium(ll) Palladium, bis(acetonitrile)dichloro- (8,9) (14592-56-4)... 

The oxidation of ds-2-hexene (II) catalyzed by palladium acetate proceeds after an induction period of 2-4 hrs shown in Figure 4. Using 0.00163M palladium acetate total inhibition of reaction was observed with 1.08 X 10 5M quinol. 2,4,6-tri (tert-Butyl) phenol (5.60 X 10 5M) only showed the reaction without total inhibition. The formation of the allylic complex IVb proceeds in a similar way to the reaction of I, and it is the major species in the catalyst solutions. The formation of unsatu-... 

Tsuji, J. Nagashima, H. Palladium-catalyzed oxidative coupling of aromatic compounds with olefins using tert-butyl perbenzoate as hydrogen acceptor. Tetrahedron 1984, 40, 2699-2702. 

A solution of 0.689 g (1.85 mmol) of 2-benzyloxycarbonyl)-N-tert-butyl-decahydro-(4aS,8aS)-isoquinoline-3(S)-carboxamide in 20 ml of ethanol was hydrogenated in the presence of 0.01 g of 10% palladium-on-carbon at room temperature and under atmospheric pressure for 18 h. The catalyst was removed by filtration and the solvent was removed by evaporation to give in quantitative yield N-tert-butyl-decahydro-(4aS,8aS)-isoquinoline-3(S)-carboxamide as a clear oil. 

An improved procedure of Suzuki-couplings was recently described by Buchwald [5] et al. By using 0-(di-tert.butyl-phosphino)-biphenyl as ligand, palladium acetate and potassium carbonate couplings are facilitated at room temperature [eq. (c)]. 

Palladium black gave the highest yield (81%) in the reduction of enamide 88 with complete stereoselectivity for C-4 epimer 102. Proof that the selectivity observed was a steric effect associated with the bulk of the C-2 tert-butyl ester was obtained by repeating the reduction with methyl ester 89. Using palladium black as a catalyst under identical conditions to those used in the reduction of 88, a 70% overall yield of products 106 and 107 in a ratio of 1 13 (isolated yield/ratio after chromatographic purification) was obtained (Scheme 45). 

Allenylsilver compounds appear to enter the palladium coupling catalytic cycle via transmetallation. It was found that tert-butyl allenylsilver, and the corresponding argentate derivative, underwent palladium-catalyzed coupling with iodobenzene to... 

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