Palladium catalysis reduction

Reduction of Acid Chlorides to Aldehydes. Palladium catalysis of acid chlorides to produce aldehydes is known as the Rosenmund reduction and is an indirect method used in the synthesis of aldehydes from organic acids. 

The intramolecular palladium catalyzed ring closure of the tetrahydro-isoquinoline derivative depicted in 8.41. led to the formation of the aporphine derivative in good yield, which was then converted into racemic aporphine in three steps. In the ring closing step 20 mol% palladium acetate and 40 mol% tricyclohexylphosphine were used as catalyst. The removal of the hydroxyl group was also achieved by palladium catalysis through its conversion to triflate and the subsequent reduction with ammonium formate in the presence of palladium acetate and dppf.53... 

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. 

Wang, C. M. Heller, A. Gerischer, H. Palladium catalysis of 02 reduction by electrons accumulated on Ti02 particles during photoassisted oxidation of organic compounds, J. Am Chem Soc. 1992, 114, 5230. 

Amino acid synthons can be prepared from iodoalanine with no loss of optical integrity (Scheme 48). The amino acid was transformed into a novel zinc reagent through reductive metallation with a zinc-copper couple in benzene/dimethyl acetamide. This organometallic was acylated under palladium catalysis in good overall yield. ... 

Ring closure of ortfto-aminoaryl-alkynyl-carbinols, readily available by acetylide addition to an aryl-ketone or -aldehyde, can be achieved with copper or palladium catalysis. Comparable ort/io-nitroaryl-carbinols undergo nitro group reduction and ring closure simply by treatment with a metal/acid combination. ... 

Moreover, methylarenes can be generated by cleavage from polystyrene resins using homogeneous palladium catalysis by either formate reduction [128] as shown in Scheme 16.32 or under an atmosphere of hydrogen [129]. 

Shimizu, S., Y. Sasaki, and C. Hirai, Inverse Phase Transfer Catalysis. Palladium-Catalyzed Reduction of Bromoanisoles with Sodium Formate, Chem Soc.Jpn.,63,176 (1990). 

We have already seen that p-bromophenol can be joined to an amine with palladium catalysis, so it should be easy to join it to piperazine. However, there is a potential problem of selectivity we want to add this benzene ring just once, and the way to do this is to protect one nitrogen atom by reductive amination with benzaldehyde. The remaining NH group can then be coupled to the aromatic ring and the benzyl group removed by hydrogenation. 

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