2.15 Ring-Closing Metathesis (RCM) for the Synthesis
of Spiroacetals
Unsaturated spiroacetals may be accessed via RCM of diene-subsituted tetrahydrofurans and tetrahydropyrans (Scheme 95).
Hsung and coworkers [191] have used simple γ- and δ-lactone-derived acetaltethered dienes (e.g. 398) in the RCM reaction (Scheme 96). This approach has
most recently been exploited for the synthesis of (+)-aigialospirol 400.
Scheme 92 Xue et al.’s HDA/IHA cascade sequence for the synthesis of bis(benzannulated)
spiroacetals [189]
Scheme 93 Reductive cyclization methods for the synthesis of spiroacetals
Synthesis of 5,6- and 6,6-Spirocyclic Compounds
253
of Spiroacetals
Unsaturated spiroacetals may be accessed via RCM of diene-subsituted tetrahydrofurans and tetrahydropyrans (Scheme 95).
Hsung and coworkers [191] have used simple γ- and δ-lactone-derived acetaltethered dienes (e.g. 398) in the RCM reaction (Scheme 96). This approach has
most recently been exploited for the synthesis of (+)-aigialospirol 400.
Scheme 92 Xue et al.’s HDA/IHA cascade sequence for the synthesis of bis(benzannulated)
spiroacetals [189]
Scheme 93 Reductive cyclization methods for the synthesis of spiroacetals
Synthesis of 5,6- and 6,6-Spirocyclic Compounds
253