Deoxygenation of tertiary and secondary alcohols ROH by thiol-catalysed radical-chain redox decomposition of derivatives ROCH2X to give RH and XCHO

Ammonium Formate/Palladium on Carbon: A Versatile System for Catalytic Hydrogen Transfer Reductions of Carbon-Carbon Double Bonds

“…The unhindered endocyclic D 2 -double bond in 5a-cholest-2-ene (15) 20 was easily reduced to 16, while the more hindered D 2 -double bond in compound 26 21 having a lanostane skeleton required 20 hours reaction time to give dihydrolanosterol (27). 22 In accord with previous data, 23 the trisubstituted D 5 -double bond in compounds 19 24 and 25 was found unreactive, as was the highly hindered D 8double bond in lanosterol (28). The The reduction of vinyl-and allyl-substituted steroids, 17 30 and 19, gave the respective saturated compounds 18 31 and 20, 32 with excellent, practically quantitative yield.…”

“…Reduction of the D 24 -double bond, quite common in triter-penoids, often required a substantial proportion of Adam's catalyst, prolonged reaction times, high temperature and/or elevated pressures. 26 Exocyclic double bond in 3-methylene-5a-cholestane (21)27 has been reduced in a fast reaction to give 3b-and 3a-methyl-5a-cholestane (2228 and 23) in the ratio 2:1, respectively. Reduction of 21 with Adam's catalyst was reported to give 22 and 23 in the ratio 1:4 29.…”

Carbohydrate chiral-pool approach to four enantiomerically pure 2-naphthylmethyl 3-hydroxy-2-methylbutanoates

“…Catalytic hydrogenation over Pd-C rather than RaNi 22 furnished a separable mixture of 6 and 7 in a proportion ca. 1:10 by 1 H NMR (roughly the same proportion of 6 to 7 was obtained using much more synthetically demanding thiol-catalyzed free-radical redox process), 23 and an unexpected monoisopropylidenated compound 8. Cleavage of 5,6-acetonide was most probably a result of the presence of small quantity of PdCl 2 in the batch of the catalyst.…”

Radicals in organic synthesis. Part 1

“…60 The use of PRC enables the deoxygenation of methoxymethyl (MOM)-protected secondary and tertiary alcohols. 70 An informative example is the deoxygenation of carbohydrate 31 (Scheme 11). Treatment of the methoxymethyl-protected alcohol with 2,2-bis(tert-butylperoxy)butane (DBPB) as radical initiator and tri-tert-butoxysilanethiol (TBST) as the polarity-reversal catalyst in the presence of collidine (coll) furnishes the desired deoxy compound 32.…”