四塩化チタンを用いるアルドール縮合の開発と展開

抄録

Aldol condensation is one of the most fundamental reactions. However, the conventional basic or acidic conditions limit the range of substrates and often lead to undesirable side reactions such as self-condensation. We have found a new one-pot aldol condensation method that consists of TiCl₄-promoted aldol reaction followed by base-promoted elimination of oxytitanium species. This method is applicable to the hitherto difficult condensations between two ketones, between thioester and ketone or aldehyde, or between selenoester and aldehyde, furnishing β,β-disubstituted α,β-unsaturated ketones, multiunsaturated thioesters, and α,β-unsaturated selenoesters. Synthetic utilities of unsaturated products in Lewis base-catalyzed conjugate reduction with HSiCl₃ and in preparation of synthetic intermediates of polyene natural products have been demonstrated. Neuroprotective activity of ar-atlantone and ar-turmrone as well as antiviral activity of α,β-unsaturated selenoesters toward HIV-1, SARS-CoV-2, and HBV have also been revealed.