Stereoselective Synthesis of Bicyclo[4.2.1]nonanes - a Temporary-Bridge Approach to Cyclooctanoids

Synthesis of Functionally Substituted Bicyclo[4.2.1]nona-2,4-dienes and Bicyclo[4.2.1]nona-2,4,7-trienes by Cobalt(I)-catalyzed [6π + 2π] Cycloaddition of 2-Tropylcyclohexanone

The [6π + 2π] cycloaddition of 2-tropylcyclohexanone to allenes and alkynes was accomplished for the first time using the three-component catalytic system Co(acac)2(dppe)/Zn/ZnI2, thus giving previously unknown functionally substituted bicyclo[4.2.1]nona-2,4-dienes and bicyclo[4.2.1]nona-2,4,7-trienes in high yields (70-89%). The structures of the synthesized carbocycles were reliably proved using modern spectral methods and X-ray diffraction. The in vitro cytotoxic activity of the obtained bicyclo[4.2.1]nona-2,4-dienes and bicyclo[4.2.1]nona-2,4,7-trienes against the Jurkat, K562, and U937 tumor cell lines has been studied.

Construction of eight-membered carbocycles with trisubstituted double bonds using the ring closing metathesis reaction

Medium sized carbocycles are particularly difficult to synthesize. Ring closing metathesis reactions (RCM) have recently been applied to construct eight-membered carbocycles, but trisubstituted double bonds in the eight-membered rings are more difficult to produce using RCM reactions. In this review, model examples and our own results are cited and the importance of the preparation of suitably designed precursors is discussed. Examples of RCM reactions used in the total synthesis of natural products are also outlined.

Highly regio- and stereocontrolled formation of functionalized tricyclo[4.2.1.0(2,8)]non-3-enes

The electrophilic activations of bicyclo[4.2.1]nonatrienes by 4-isopropyl-1,2,4-triazolinedione, N-iodosuccinimide, or an epoxidation/acidic ring-opening sequence is reported. The subsequent in situ trappings by water, alcohols, or benzoic acids led to original tricyclo[4.2.1.0(2,8)]non-3-enes with high regio- and stereoselectivities. The synthetic potentiality of these synthons is illustrated by the straightforward access to a fused cyclopropane featuring six consecutive controlled stereocenters.