Synthesis and herbicidal application of turpentine derivative p-menthene type secondary amines as sustainable agrochemicals

Abstract

Compound 3a showed excellent herbicidal activity against barnyard grass with IC50 = 7.0 mg L−1, and exhibited good selection for rice, wheat, and radish at 100 mg L−1.

Synthesis, Herbicidal Activity and Toxicity Evaluation of Secondary Ammonium Salts from Turpentine Oil for Sustainable Weed Control

“…p‐ Menth‐3‐enylamine ( 5 ) is a novel monoterpene amine synthesized in very recent years, which can be prepared from N , N '‐diacetyl‐ p ‐menthane‐1,8‐diamines ( 8 ) by two steps as an acid‐catalyzed elimination and alkaline‐catalyzed hydrolysis [20] . Our previous research has successfully synthesized a series of amine derivatives of cis‐ 1,8‐ p ‐menthane‐diamine and p‐ menth‐3‐enylamine and found the secondary amine derivatives ( 6a – 6l , 9a – 9i ), such as N‐ (4‐fluorobenzyl)‐4‐isopropyl‐1‐methylcyclohexane‐3‐enamine ( 6a ), exhibited excellent herbicidal activities toward some noxious weeds [16] . However, it is inevitable to add organic solvents and additives during herbicidal applications because all the above secondary amines are either oily liquid or solid powder with low water solubility.…”

“…p ‐Menth‐3‐enylamine, cis‐ 1,8‐ p ‐menthane‐diamine, and p‐ menthene‐7‐amine secondary amines were synthesized from α / β ‐pinene in our laboratory following literature procedures [16,17] . Other chemicals and reagents were commercially available and used without further purification.…”

“…[20] Our previous research has successfully synthesized a series of amine derivatives of cis-1,8-p-menthane-diamine and p-menth-3-enylamine and found the secondary amine derivatives (6a -6l, 9a-9i), such as N-(4-fluorobenzyl)-4-isopropyl-1-methylcyclohexane-3-enamine (6a), exhibited excellent herbicidal activities toward some noxious weeds. [16] However, it is inevitable to add organic solvents and additives during herbicidal applications because all the above secondary amines are either oily liquid or solid powder with low water solubility. Considering the potential toxicity of organic solvents, a chloride anion was introduced to the NÀ H secondary amine of cis-1,8-p-menthane-diamine and p-menth-3enylamine to afford corresponding ammonium 7a-7l and 10a -10i in 58.5 -93.5 % yields.…”

“…According to our previous study, p‐ menthane and p‐ menthene secondary amine compounds, including sec ‐ p ‐menth‐3‐enylamines, sec ‐ is ‐1,8‐ p ‐menthane‐diamines, and sec ‐ p ‐menthene‐7‐amines all possess low toxicity, potential herbicidal efficacy, and a broad spectrum against some noxious weeds [16–20] . However, the poor water‐solubility of these amine derivatives caused concerns in herbicidal applications, such as the overdose of herbicidal active substances and the excessive use of organic solvents and additives, which will have adverse effects on large‐scale application and sustainable development.…”

Design, synthesis, and herbicidal activity of sec-p-menthane-7-amine derivatives as botanical herbicides

“…It has been proven that secondary amines such as sec-p-menth-3-enylamines and cis-1,8-p-menthane-di-sec-amines exhibit higher herbicidal activities than that of Schiff bases, and they show low toxicity to common crops and mammal cells. 26,27 Perillaldehyde is a natural monoterpene of the p-menthane group originating from plant Perilla frutescens. It was reported that perillaldehyde displayed various bioactivities such as antidepression and antibacterial activity, 28,29 but the herbicidal activity is rarely reported.…”