Access to Polyfunctionalized Diquinanes, Hydrindanes, and Decalines via TiCl₄ Promoted Michael–Aldol and Baylis–Hillman Reactions

The addition of 0.5 equiv of TiCl4 to (cyclo)alkanones tethered to α,β-unsaturated ketones afforded polyfunctionalized diquinanes, hydrindanes, and decalines. These products, resulting from a Michael–aldol or a Baylis–Hillman reaction, can be obtained with high or total diastereoselectivity in moderate to high yields. These scaffolds represent interesting building blocks for the synthesis of complex natural products.