An Easy Access to γ-Lactone-Fused Cyclopentanoids

Abstract

The tricyclic alpha-keto hemiacetals 3a,b and 8a-d obtained from ruthenium-catalyzed oxidation of tetrahalonorbornyl derivatives possessing a pendant hydroxymethyl group were cleaved using Pb(OAc)(4) or alkaline H(2)O(2) to give gamma-lactone-fused cyclopentane derivatives 5a,b and 9a-d. The alpha-keto hemiacetal 3b has also been elaborated to spiroepoxide derivative 25. The stable hydrate 4 formed from ruthenium-catalyzed oxidation of acrolein adduct 10 furnished an intramolecular hemiacetal 11 upon cleavage with Pb(OAc)(4). The alpha-halo ester moiety in 5a was transformed smoothly in a highly regio- and stereoselective manner to alpha-hydroxy esters through a lactone-assisted intermediate to furnish 18.

Sequential Catalysis: A Metathesis/Dihydroxylation Sequence

“…A variety of ruthenium sources, such as RuCl 3 , [12] RuO 2 , [13] [RuCl 2 (dppp) 2 ] (dppp = 1,3-bis(diphenylphosphanyl)propane), [14] [RuCl 2 (PPh 3 ) 3 ], [15] [Ru(acac) 3 ] (acac = acetylacetonate) [15] TPAP (tetrapropylammonium perruthenate), [15] and Ru/C, [15] have been used for the formation of the oxidative species RuO 4 in different oxidation reactions. [16] The method of choice for dihydroxylation of olefins is in situ formation from a catalytic amount of RuCl 3 ·3 H 2 O using NaIO 4 as the stoichiometric oxidant.…”

Studies towards the synthesis of hyperireflexolide A

“…Previously, we reported from our laboratory the synthesis of γ-lactone-fused cyclopentane derivative 5 from the respective Diels–Alder adduct in 5 steps with an overall yield of 29% [32]. Hydrolysis of dimethyl ketal 5 with MeSO 3 H in 1,2-DCE furnished γ-lactone-fused cyclopentanone 6 in 97% yield.…”

“…Earlier from our lab, we reported a short and efficient methodology for the synthesis of γ-lactone-fused cyclopentane 5 [32]. The cis -ring junction of this carbocylic ring system offers a high degree of selectivity for the assemblage of various substituents on the convex surface.…”

Indium‐Mediated Regio‐ and Diastereoselective Reduction of Norbornyl α‐Diketones

“…Following the initial indium-mediated reduction, intramolecular displacement occurred to furnish the alcohol 31 as the major product and oxa tricycle 27 as the minor one. The fact that reaction proceeds via the reduction of the a-diketone 1 h was further proved by separately treating the a-keto hemiacetal 30 [19] with indium in aqueous MeOH under reflux conditions for 42 h. The attempted reaction failed to give 26 and the starting material was recovered (Scheme 6).…”

“…[19] While discrimination between the two reducible moieties, that is to say the ester and lactone groups of lactone derivative 25, would be difficult, by carrying out a cleavage reaction after indium-mediated reduction of 1 h, such a distinction is possible. Indeed, cleavage of the diol 26 with lead tetraacetate in MeOH/PhH (3:1) furnished the fused g-lactone cyclopentanoid derivative 29, [19] having groups distinctively different in reactivity towards hydride-based reducing agents, thereby providing a handle for selective transformation.…”