Palladium hydroxy group effect

Hydrogenation of 19-hydroxy-3a- and 3j5-substituted-A -steroids over platinum or rhodium yields increased amounts of 5j9-products as compared to the corresponding 19-desoxy series (hydroxyl group effect). In contrast, the A -19-carboxaldehyde (27) gives only the 5a-product when hydrogenated over either palladium or platinum. ... 

A synthesis of 5-(alkyn-l-yl)-l,2,4-triazines 77 has been developed, in which, by activation with the palladium-containing catalyst, acetylenes effectively react with 5-chloro- and 5-iodo-l,2,4-triazines 76 (Scheme 46) (84H2245). The synthesis of 5-((o-alkynyl)-l,2,4-triazines 79 has been described using as nucleophile acetylenes 78 featuring a nucleophilic group (e.g., hydroxy or CH-activated group) (Scheme 46). 

The positive effect of the electron-withdrawing substituent in the ortho position also allowed the use of the corresponding bromide in place of the iodide with comparable yields although for a longer time. Too-bulky groups such as t-butyl led to the exclusive formation of the hexahydromethanobiphenylene compound shown in Sect. 4.1, Eq. 33. Groups that interfere with palladium in arylnorbornylpalladium complexes, such as mono- and dimethylamino, hydroxy and acetoxy, inhibited the reaction. 

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