Allyl acetates palladium catalysis

Synthesis of isomeric chiral protected (63 )-6-amino-hexahydro-2,7-dioxopyrazolo[l,2- ]pyrazole-l-carboxylic acid 280 is shown in Scheme 36. Crude vinyl phosphonate 275, obtained by treatment of diethyl allyloxycarbonylmethyl-phosphonate with acetic anhydride and tetramethyl diaminomethane as a formaldehyde equivalent, was used in the Michael addition to chiral 4-(f-butoxycarbonylamino)pyrazolidin-3-one 272. The Michael addition is run in dichloro-methane followed by addition of f-butyl oxalyl chloride and 2 equiv of Huning s base in the same pot to provide 276 in 58% yield. The allyl ester is deprotected using palladium catalysis to give the corresponding acid 277, which is... 

Both the palladium- and the nickel-catalysis enables the use of allylic acetate as starting reagent. In the two approaches a zinc compound is evoked as key intermediate, though its formation has been demonstrated only indirectly. In the two methods allylic transposition is observed. The authors have then concluded that these electrochemical allylation reactions closely parallel the chemical allylation reactions involving allylzinc intermediates. 

In the palladium-catalyzed addition of allylstannanes to allyl acetates, complete allyl inversion of the allylstannane is observed.137 Symmetrical coupling is also possible, for example, by treatment of cinna-myl acetate with hexa-n-butyldistannane.137 In this reaction, cinnamyl tri-n-butylstannane is generated in situ by Pd catalysis and it then couples with the allyl acetate with allyl inversion (equation 32). 

The desymmetrization of dicarbonate 206 was initiated by the addition of one equivalent of N-(3-butenyl) nosylamide 207 under palladium catalysis in the presence of Trost s chiral diphosphine ligand 205. When the first allylic substitution was completed, the reaction was warmed and the resulting intermediate 208 was treated in situ with one equivalent of a second nosylamide 209. Product 210 resulting from this double substitution reaction was submitted to a tandem intramolecular ROM/RCM to furnish key precursor 211, which was engaged in the final cyc-lization step by the reduction of the double bonds, followed by the HCl-promoted domino deprotection of the acetal and aminal formation. 

Palladium(II) catalysis (0.01-0.04 equiv) is more effective and leads to higher selectivity than mercury(II) catalysis912. With bis(acetonitrile)palladium(II) chloride [Pd(CH3CN)2CI2] as catalyst the efficiency decreases in the order carbamates > allylic acetates > carbonates. 

Since vinyl stannanes (chapter 18) couple with electrophiles under catalysis by Pd(0), it makes sense to create the electrophile by the palladium-catalysed reactions of allylic acetates in the same pot.50 The vinyl stannane 304 reacts cleanly with the more complex allylic acetate 305 with 0.2 equivalents of Pd(0) to give the triene 306 in good yield.51... 

Chiral bisoxazoline associated with palladium is a very efficient organometallic catalyst for the asymmetric allylic alkylation of allylic acetates and carbonates, allowing the formation of carbon-carbon as well as carbon-heteroatom bond in enantiomeric excesses higher than 95%.[1,2] However one of the problems in organometallic homogeneous catalysis is the separation of the catalyst, often toxic and very expensive, from the product(s) of the reaction. Very recently, a chiral fluorous bisoxazoline (Figure 3.1) has been shown to be an efficient ligand in the... 

Aryl-, alkenyl- and alkynylpalladium species readily undergo carbonylation reactions because carbon monoxide as a loosely bonded ligand can reversibly insert into any palladium-carbon bond [110]. Thus, 2-allyl-l-iodocyclopentene (148), under palladium catalysis, reacts with carbon monoxide in two modes, depending on the excess of carbon monoxide and the catalyst cocktail (Scheme 3-39) [110a]. With a slight excess (1.1 atm of CO) in the presence of [Pd(PPh3)4] in tetrahydrofuran, 148 cyclized with one CO insertion to yield 3-methylenebicyclo[3.3.0]oct-l(5)-en-2-one (152), and under 40 atm of CO with [Pd(PPh ,)2Cl2] in benzene/acetonitrile/methanol, methyl 2- 3 -(2 -oxobicyclo[3.3.0]oct-1 (5 )-enyl) acetate 149 after two CO insertions (Scheme 3-39). 

Couplings WS Allyl Intermediates- Excellent reviews cover selectivities and mechanism in palladium catalysed allyl reactions. General examples of NaCH(CX)2R)2 additions to allyl acetates, carbonates, and chlorides have appeared. Trifluotoacetale is the preferred leaving group for retention of (E)/( stereochemistry in the case of substituted allyls. Ketomalonates are susceptible to diallylation under PdL2 catalysis especially in the presence of diacetates whidi prove effective routes to bicyclic systems (Equation 6). ... 

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