One‐Pot Gold(I)‐Catalyzed Rautenstrauch Rearrangement/Nitrosocarbonyl Hetero‐Diels–Alder Reaction Sequence for the Synthesis of α‐Hydroxylated Cyclopentenones

The synthesis of densely functionalized, ring‐fused α‐hydroxy‐2‐cyclopentenone precursors is achieved by one‐pot gold(I)‐catalyzed Rautenstrauch/hetero Diels−Alder/ring opening sequential reactions of suitable propargyl esters. The 1,2‐acyloxy migration/cyclization process (Rautenstrauch reaction) leads to cyclopentadienyl ester intermediates which are stereo‐ and regioselectively trapped by the nitrosocarbonyl reagent generated in situ by adding a hydroxamic acid (e.g., Boc‐NHOH) and an oxidant ( n ‐Bu 4 NIO 4 ) to the reaction mixture after the Au(I)‐catalyzed cycloisomerization step. This provides strained intermediates, which undergo highly regioselective ring opening by a retro‐aza‐Michael reaction triggered by hydrolysis of the acetate group, eventually yielding the precursors of racemic, ring‐fused α‐hydroxy‐2‐cyclopentenone compounds in 46%–90% yield. The target six‐, seven‐, and eight‐membered ring‐fused cyclopentenones bearing a tertiary α‐hydroxy group can be then obtained in moderate to good yield (42%–84%) by N‐O cleavage in the presence of Mo(CO) 6 .