Tandem Cyclization of α-Cyano α-Alkynyl Aryl Ketones Induced by tert-Butyl Hydroperoxide and Tetrabutylammonium Iodide

Abstract

The radical cascade protocol of the α-cyano α-TMS/aryl-capped alkynyl aryl ketones promoted by tert-butyl hydroperoxide under catalysis with tetrabutylammonium iodide in refluxing benzene has been developed, leading to the construction of a variety of highly functionalized [6,6,5] tricyclic frameworks in an efficient manner.

The Total Synthesis of Retrojusticidin B, Justicidin E, and Helioxanthin

“…4b,14 In continuation of our studies on the synthesis of natural and unnatural lignan for new drug screening, we have developed several efficient cyclization processes to have facile access to linear [6,6,5] or [5,6,5] tricyclic systems (Scheme 1). [15][16][17] These protocols are currently extended to the synthesis of various natural products containing either cyclopenta [b]naphthalene or benzo [b]fluorene skeletons, such as stealthins and kinamycins. 18 In addition, it was discovered that instead of using α-cyano ketones as substrates, Encouraged by the success of the model study, the synthesis of retrojusticidin B was then attempted following the similar approach starting from alkynol 5, commercially available or readily prepared according to the procedure reported in the literature.…”

Iodine in Modern Oxidation Catalysis

“…With 20 mol% of tetrabutylammonium iodide and again tert-butyl hydroperoxide as co-oxidant, the tricyclic structures 62 were obtained by a radical cascade process. 71 Scheme 33 Tandem cyclization of α-cyano-α-alkynyl aryl ketones mediated by tetrabutylammonium iodide and tert-butyl hydroperoxide An efficient tetrabutylammonium iodide mediated oxidative C3-formylation of indoles 63 with N-methylaniline (64) was developed by Wang and co-workers (Scheme 34). 72 With tert-butyl peroxybenzoate (TBPB) as co-oxidant, the desired C3-formylated indoles 65 were isolated in up to 82% yield.…”

Manganese(III)‐Catalyzed Oxidative Cyclization of Aryl 1‐Cyanoalk‐5‐ynyl Ketone Systems: A Convenient and General Approach to Cyclopenta[b]naphthalene Derivatives

“…α‐Cyano ketones 1 (Scheme ) are found to undergo tandem cyclization with ease to afford the corresponding cyclopenta[ b ]naphthalene derivatives 2 under the reaction conditions ( a ) or ( b ) previously developed by us 3,4…”