Reaction conditions: 0.15 mmol BCB ketone 1a (1.0 equiv), 0.33 mmol silyl dienol ether 2a-a'' (2.2 equiv.), Lewis acid (X mol%), in With an optimized protocol in hands, we then assessed the generality of our method (Scheme 3). We started by considering variations of the BCB ketone substrates. Aryl-substituted BCB ketones were initially studied (Scheme 3A). A further five-fold scale-up of the reaction to 1.5 mmol of 2a produced 4aa in 80% yield, demonstrating the excellent reproducibility of the procedure. Phenyl ketone 1b afforded BCO 4ba in 84% yield. An electron-donating methoxy substituent on the aromatic ring was also tolerated in both the para (4ca, 84% yield) and the meta (4da, 73% yield) positions. With an ortho OMe group, BCO 4ea was isolated in 57% yield. Electron-withdrawing substituents were also compatible, albeit longer reaction times were necessary: substrates having a bromine atom, a trifluoromethyl, or a nitrile in the para position of the aryl group gave BCO derivatives 4g-ia in 60-70% yield. Thiophene-containing BCB 1i gave 4ia in 70% yield. Then, BCBs with substituents on the bridgehead of the bicycle were examined (Scheme 3B). A methyl was poorly tolerated as product 4ja was obtained in only 15% yield. BCB 1k, containing a phenyl at the bridgehead carbon, was converted into 4ka in 35% yield. In the presence of more electron-poor 3,4-difluorophenyl and 4-trifluoromethyl phenyl groups, products 4la and 4am were generated in 39% and 58% yields. Finally, alkyl BCB ketones were also good starting materials (Scheme 3C): a primary n butyl, a secondary and cyclic cyclohexyl, and a tertiary t butyl groups on the carbonyl of the substrate were all tolerated, furnishing aliphatic BCO 4na, 4oa and 4pa in 59%, 77% and 57% yields, respectively. X-ray diffraction of 4pa gave a confirmation of the caged bicyclic framework of the synthesized BCO derivatives. We then turned our interest towards varying the TBDPS dienol ether in the reaction with 1a (Scheme 3D). Unsubstituted 2b and 1-methyl substituted 2c both gave corresponding BCO derivative, 4ab and 4ac, in modest yields (27% and 34%). Diene 2dcontaining methyl groups in both C1 and C3also gave a moderated yield butinterestinglyproduct 4ad was formed as a single trans diastereoisomer, as determined by X-Ray diffraction. In the case of a diene bearing a methyl group in C4, the expected BCO 4ae was not formed and only a complex mixture was observed. With one substituent in C3 position, the reaction worked consistently well with different substituents. Alkyl groups were all tolerated: benzyl-containing BCO 4af was synthesized in high 75% yield, whereas 4ag and 4ahwith a n butyl and a cyclohexyl groupswere delivered quantitatively and in 77% yield. With aryl C3-substituted dienes, readjusting the procedure was necessary: a slightly decreasing the amount of the dienol ether to 2.0 equivalents was possible, but a longer reaction time was needed, together with a larger excess of TMS-OTf during the silyl-deprotecting work-up. With diene 2i bearing an electron-rich p-anisyl group in C3, 4ai was obtained in 71% yield. Heterocyclic diene 2j gave benzofuran-substituted BCO 4aj in 61% yield. Slightly lower yields were obtained with dienol silyl ethers bearing less electron-donating aryl substituents: 4ak and 4am were accessed in 55% and 56% yields. [a] Performed on 1.5 mmol scale. [b] The reaction was run overnight. [c] Average yield over two reiterations.