Synthesis and antifeedant activity of 3H-indole derived oxime esters and oxime ethers against cotton bollworm

Abstract

The O-acylation or O-alkylation of 3H-indole derived oximes is conveniently synthesized from indoles and the corresponding anhydrides or alcohols mediated by tert-butyl nitrite (TBN) under mild conditions. O-Acyloxime esters are obtained with yields up to 82% using anhydrides via a facile one-pot reaction. Fluorinated O-alkyloxime ethers are achieved with yields up to 38% using fluorinated alcohols through an optimized step-by-step strategy or a 2,2,6,6-tetramethylpiperidinyl-1-oxide (TEMPO)-assisted one-pot strategy. Meanwhile, the better reaction yields, up to 64%, are achieved for nonfluorinated O-alkyloxime ethers. These approaches allow access to a diversity of O-acyloxime esters and fluorinated/nonfluorinated O-alkyloxime ethers, underscoring broad substrate scopes, good functional tolerance and easily gram-scale. All the synthesized compounds were evaluated for their potential antifeedant activity and 5f shows good antifeedant activity against cotton bollworm with a negative logarithmic effective concentration for 50% feeding reduction (pEC50) at 4.217.