Palladium acetate diols

Palladium acetate with bromobenzene as cooxidant will oxidize primary a,o>-diols (27 equation 27) and (28 equation 28) to lactones, but as can be seen from the examples given, the selectivity in unsym-metrical cases is rather low. ... 

The cyclization o-phenylenediamine with 2-butene-1,4-diol catalyzed by palladium acetate coordinated with (7 )-BINAP as the chiral ligand leads to optically active 1,2,3,4-tetrahydro-2-vinylquinoxaline with 19ee and 58% yield [117]. 

An organobase including guanidine is often used as co-catalyst (or base) in palladium coupling reactions [84]. The 2-methylenepropane-l,3-diol diacetate reacts with 7,8-dihydroquinoline derivative in the presence of palladium acetate [Pd(OAc)2], TMG (1) and triphenylphosphine (PPhs) to give the methylene bridged compound in 92% yield, which can be converted to a diamino analogue of huperzine A, an inhibitor of acetylcholine esterase [84a](Scheme 4.32). 

Enantiopure alkenyl iodide 35 reacts with the unprotected diol 34 in the presence of palladium acetate to provide cyclopentanone 36 plus a diastereomer in 15% yield. 

CH2=C(OBn)CH2F, PdCl2(COD), CH3CN, it, 24 h, 89-100% yield. Protic acids can also be used to introduce this group, but the yields are sometimes lower. A primary alcohol can be protected in the presence of a secondary alcohol. This reagent also does not give cyclic acetals of 1,3-diols with palladium catalysis. 

Reduction of 17a-EthynyI to 17a-Ethyl °° A solution of 5 g of 17a-ethynyl-androst-5-ene-3j9,17j5-diol in 170 ml of absolute alcohol is hydrogenated at atmospheric pressure and room temperature using 0.5 g of 5 % palladium-on-charcoal catalyst. Hydrogen absorption is complete in about 8 min with the absorption of 2 moles. After removal of the catalyst by filtration, the solvent is evaporated under reduced pressure and the residue is crystallized from ethyl acetate. Three crops of 17a-ethylandrost-5-ene-3) ,17j9-diol are obtained 3.05 g, mp 197-200° 1.59 g, mp 198.6-200.6° and 0.34 g, mp 196-199° (total yield 5.02 g, 90%). A sample prepared for analysis by recrystallization from ethyl acetate melts at 200.6-202.4° [aj, —70° (diox.). 

Another route to the diol monomer is provided by hydroformylation of allyl alcohol or allyl acetate. Allyl acetate can be produced easily by the palladium-catalyzed oxidation of propylene in the presence of acetic acid in a process similar to commercial vinyl acetate production. Both cobalt-and rhodium-catalyzed hydroformylations have received much attention in recent patent literature (83-86). Hydroformylation with cobalt carbonyl at 140°C and 180-200 atm H2/CO (83) gave a mixture of three aldehydes in 85-99% total yield. 

In the synthesis of the head-to-head [4 + 4] dimer of cyclopentadiene, the preferential reductive fission of the C3-C4 bond in bishomocubane again plays a significant role.43 Thus, catalytic hydrogenation of bishomocubane-6,10-diol (14) over 10% palladium on charcoal in ethyl acetate at 2.7-3.4 atmospheres for two days furnished the bishomosecocubanediol tetracy-clo[5.2.1.02,< .04 8]decane-5,10-diol (15).43... 

Compound 85 was dehydrogenated at 300° over palladium black under reduced pressure to a pyridine derivative 96 which was independently synthesized by the following route. Anisaldehyde (86) was treated with iodine monochloride in acetic acid to give the 3-iodo derivative 87. The Ullmann reaction of 87 in the presence of copper bronze afforded biphenyldialdehyde (88). The Knoevenagel condensation with malonic acid yielded the unsaturated diacid 91. The methyl ester (92) was also prepared alternatively by a condensation of 3-iodoanisaldehyde with malonic acid to give the iodo-cinnamic acid (89), followed by the Ullmann reaction of its methyl ester (90). The cinnamic diester was catalytically hydrogenated and reduced with lithium aluminium hydride to the diol 94. Reaction with phosphoryl chloride afforded an amorphous dichloro derivative (95) which was condensed with 2,6-lutidine in liquid ammonia in the presence of potassium amide to yield pyridine the derivative 96 in 27% yield (53). 

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