A regiospecific route to conjugated enones viaα-phenylthio ketones

Highly Enantioselective Iridium‐Catalyzed Hydrogenation of α,β‐Unsaturated Esters

“…The asymmetric hydrogenation of ( Z )‐ethyl 3‐( p ‐tolyl)but‐2‐enoate 39 gave ( S )‐ethyl 3‐( p ‐tolyl)butanoate 40 as a single enantiomer in 98 % yield (Scheme ). This can be transformed to ( S )‐3‐( p ‐tolyl)butanal 41 ,37 which has been used in the total syntheses of (+)‐Dehydrocurcumene, (+)‐Curcumene, and (+)‐Tumerone 38. Ester 40 could also be converted to 4‐( p ‐tolyl)pentanal 42 ,39 a precursor in the syntheses of (+)‐Nuciferol, (+)‐Nuciferal, and (+)‐Erogorgiaene 40…”

Novel non-classical C9-methyl-5-substituted-2,4-diaminopyrrolo[2,3-d]pyrimidines as potential inhibitors of dihydrofolate reductase and as anti-opportunistic agents

“…20 The total yield for this two step procedure was reasonably good (40%) for 46, but purification of the compounds remained a problem, and the use of impure aldehyde for the subsequent step was not feasible. In view of the fact that the ester could be reduced to the corresponding aldehyde with DIBAL-H, an alterate synthetic approach was adopted in which the double bond of the α,β-unsaturated esters 32-36 were reduced by catalytic hydrogenation, 21 followed by reduction with DIBAL-H to afford the aldehydes 42-46 in very high yield (two steps >80%, Scheme 3). 22 The Henry reaction of aldehydes 42-47 with nitromethane gave the expected nitro alcohol intermediates 48-53 (Scheme 4).…”

Transformation of thiols to disulfides by epolactaene and its derivatives

“…We considered that a retro-Claisen reaction of b-hydroxy-c-lactam derivative 10 or 11 might occur under the basic conditions (Scheme 6). 32, 33 We decided to prepare each compound by a coupling of methyl glyoxal and b-ketoamide derivatives. Reaction of 6b with methyl glyoxal in a 1:1 MeOH/0.5 M NaH-CO 3 aq solution gave dodecanoic acid 4b in quantitative yield (Scheme 7A).…”