Pyridines synthesis, palladium® chloride

Carboxylation of dienes and trienes, which takes place in a stepwise fashion, affords mono- or dicarboxylated products.146 Cobalt carbonyl,147 palladium chloride,148 149 and palladium complexes150 were used. 1,4 Addition to 1,3-butadiene gives the corresponding unsaturated tram ester (methyl trans-3-pentenoate) in the presence of [Co(CO)4]2 and a pyridine base.147 The second carboxylation step requires higher temperature than the first one to yield dimethyl adipate. In a direct synthesis (110°C, 500 atm, then 200°C, 530 atm) 51% selectivity was achieved.147... 

For example, a bioinspired oxidation with hydroperoxy-flavins 590 combined with a catalyst-free 1,4-dihydropyri-dine synthesis effectively produces C4-unsubstituted pyridines 591 (Scheme 13.147) [267], whereas a palladium on carbon oxidation combined with an MK-10 catalyzed 1,4-dihydropyridine formation under microwave assistance reduces the reaction time (Scheme 13.148) [268]. A one-pot performance of the pyridine synthesis is also possible in water with stoichiometric soluble oxidants like iron chloride or potassium permanganate (Scheme 13.148) [266]. Nevertheless, both examples (Scheme 13.148) cleave off... 

One of the first compounds to be introduced to the clinic, aztreonam (40-9), has been produced by total synthesis. Constmction of the chiral azetidone starts with amide formation of L-threonine (40-1) via its acid chloride treatment with ammonia leads to the corresponding amide (40-2). The primary amino group in that product is then protected as its carbobenzyloxy derivative (40-3). Reaction of that product with methanesulfonyl chloride affords the mesylate (40-4). Treatment of that intermediate with the pyridine sulfur trioxide complex leads to the formation of the A -sulfonated amide (40-5). Potassium bicarbonate is sufficiently basic to ionize the very acidic proton on the amide the resulting anion then displaces the adjacent mesylate to form the desired azetidone the product is isolated as its tetrabutyl ammonium salt (40-6). Catalytic hydrogenation over palladium removes the carbobenzyloxy protecting group to afford the free primary amine (40-7). The... 

MUller reports a four component, one-pot synthesis of pyridines <02TL6907>. For example, aryl halide 15 and propargylic alcohol 16 were combined in the presence of copper and palladium to afford enone 17. The addition of cyclic enamine 18 led to Michael addition and the subsequent cyclocondensation was achieved by adding ammonium chloride and acetic acid (19—>20). Other multicomponent approaches to substituted pyridines have been reports by Litvinov <02RCBIE362>, Elkholy <02SC3493> and Veronese <02T9709>. 

The reactions proceed with retention of configuration at phosphorus. Various classical routes to alkylphosphine oxides have been applied in the synthesis of a range of potentially chelating and pincer-like ligands, e.g., (233), the binaphthyl system (234), the hybrid phosphine oxide-N-oxide (235), and the chiral pyridine bis(phosphine oxide) (236). A route to diarylmethylphosphine oxides is afforded by the palladium-catalysed reaction of aryl bromides with tet-rakis(hydroxymethyl)phosphonium chloride in the presence of a base. The diastereoisomeric system (237) has been isolated from the reaction of a cyclic... 

Pyridine reacts with synthesis gas at 212 C and 1150 psi in the presence of Co(0) catlaysts to produce N-formyl-, Njmethyl-, N.-ethyl-, and ji-propylpiperidine . THe hydrocarbonylation of e-substituted tJ-vinylphthalimides by Rh or Pd complexes is strongly affected by the substituent . A palladium catalysed synthesis of 6,y-unsaturated aldehydes from chloride or bromide precursors is reported (eg reaction 13) . ... 

Another formal synthesis of (5 ,9. -(—)-indolizidine 223AB (1780), by Charette and colleagues, employed a valine-derived auxiliary as an amide-containing appendage in the pyridine (—)-1788 in order to control absolute stereochemistry (Scheme 225). An unusual cyclization mediated by trifluor-omethanesulfonic anhydride followed by addition ofpropylmagnesium chloride afforded the (fo)-bicyclic amidine (—)-1789. Diastereoselective hydrogenation over palladium on carbon produced the saturated indolizidine (—)-1790, which was alkylated with iodomethane to give the amidinium salt... 

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