A silver(I)-catalyzed method to access spiro-pyrrolidinedioneoxiranes has been developed. Silver hexafluoroantimonate was found to be an efficient catalyst for the epoxidation of aldehydes using donor-/acceptor-substituted vinyl diazosuccinimides as carbenoid precursors. The protocol has been found to be highly regio-and chemoselective, and works well with aromatic aldehydes containing electronwithdrawing and -donating groups to afford spiro-pyrrolidinedioneoxiranes with a broad substrate scope. Dr. Homi
A de novo protecting-group-free total synthesis of (+)-muricadienin, (+)-ancepsenolide and (+)-3-hexadecyl-5-methylfuran-2(5H)-one has been achieved. Ring-closing-metathesis has been the key step in the synthesis. In (+)-muricadienin synthesis, a long chain alkyl group has been installed by an sp-sp Sonogashira type reaction followed by a cis-selective Lindlar reduction. The total synthesis is achieved in 7 steps and in excellent 43.5% overall yield. Similarly, (+)-ancepsenolide and (+)-3-hexadecyl-5-methylfuran-2(5H)-one synthesis is completed in 5 steps each and in 48 and 68% overall yields, respectively.
A silver triflimide catalyzed one‐pot protocol for the diastereoselective synthesis of dihydrobenzoxepines has been developed. Silver triflimide was found to be an efficient catalyst for the formal (5+2)‐cycloaddition to access dihydrobenzoxepines as a single diastereomer using vinyl diazosuccinimides as 5‐C‐synthons and ketones. An unmet challenge of utilizing the donor‐/acceptor‐type vinyl diazosuccinimides as 5‐C‐synthons under silver‐catalysis is presented. This protocol was found to be highly regio‐, chemo‐ and diastereoselective, and works well with aliphatic as well as aromatic methyl ketones bearing electron deactivating as well as donating groups to afford dihydrobenzo[5,6]oxepino[2,3‐c]pyrroles. The control experiments and time‐dependent NMR studies revealed the plausible mechanism of this transformation. The protocol also proved to be scalable on the gram‐scale synthesis.
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