New Methods For Cyclopentannulation
A non-exhaustive introduction to well-established synthetic approaches toward cyclopentannulation is illustrated, which relies on modern aspect reported in between 2003 to present year. Next, our investigations on the validity of novel stereoselective cyclopentannulation are outlined. Preliminary studies on nucleophilic catalysis toward the synthesis of cyclopentenone conducted us to the discovery of a new reagent-free protocol for Nazarov cyclization that produces highly substituted cyclopentenones in good to excellent yields. These neutral reaction conditions may enable the extension of Nazarov methodology to acidsensitive substrates that have been previously inaccessible. We have also developed the intramolecular iodo-aldol cyclization of enoate aldehydes and ketones to afford quaternary centre containing hetero and carbocycles. The reaction transforms simple, pro-chiral starting materials into cyclic alcohols, containing vicinal quaternary and secondary/tertiary stereocentres, in good yields with excellent stereoselectivity. In addition, the products display a collection of orthogonal functional groups that may be further elaborated in the synthesis of complex natural product targets. Finally, we have produced 5-monosubstituted tetronic acid derivatives through a simple and selective Pd-π-allyl-mediated cyclization. Although catalytic and asymmetric aspects of the reaction remain to be investigated, these preliminary may be incorporated into a racemic synthesis of the natural product vertinolide.