Regio- and stereochemically controlled formation of hydroxamic acids from indium triflate-mediated nucleophilic ring-opening reactions with acylnitroso-Diels–Alder adducts

Treatment of acylnitroso-Diels–Alder [2.2.1] bicyclic adducts 2a–b with indium triflate in an alcohol solvent induces ring-opening reactions to afford monocyclic anti-1,2-, anti-1,4-, and syn-1,4-hydroxamic acids with good to excellent regio- and stereoselectivity (up to 7:86:7). Treatment of [2.2.2] bicyclic nitroso adducts 2c–d under similar reaction conditions generates only anti-1,2- and anti-1,4-hydroxamic acids with anti-1,4-product being predominant (up to 17:83).