Isopropyl Cresols: Synthesis and Herbicidal Activity

Abstract

Isopropyl cresols were prepared by a two-step process: monoterpene oxidation catalyzed by CrO 3 and terpenone isomerization catalyzed by 13X molecular sieves. 5-Isopropyl-3methylphenol and carvacrol were prepared from 3-carene, whereas thymol and 4-isopropyl-3-methylphenol were synthesized from α-pinene. The two reactions followed an identical procedure, but the reaction of 3-carene was more efficient, benefiting from the three-membered ring in the structure. 5-Isopropyl-3-methylphenol, thymol, and carvacrol were found to show higher herbicidal activity than glyphosate toward the root growth of barnyard grass. However, they exhibited slightly lower activity in preventing shoot growth. Moreover, 5isopropyl-3-methylphenol showed higher herbicidal activity than its isomers, which indicates that the relative position of substitutes is significantly associated with the herbicidal activity of isopropyl cresols.[a] J.

Conformational Space, IR-Induced, and UV-Induced Chemistry of Carvacrol Isolated in a Low-Temperature Argon Matrix

“…13−16 Such a wide range of biological properties makes carvacrol a very promising compound to be used in clinical practice. 11,15 Moreover, it also finds important applications as an insecticide, 17 a herbicide, 18 and in the cosmetic and food industries as a component to produce fragrances and flavor additives. 19,20 Because of its vast number of biological and pharmacological applications, carvacrol has been the object of numerous in vivo and in vitro investigations.…”

“…Carvacrol (5-isopropyl-2-methylphenol, see Figure ) is a natural phenolic monoterpene, biosynthesized by aromatization of γ-terpinene (1-isopropyl-4-methyl-1,4-cyclohexadiene) to p -cymene (1-isopropyl-4-methylbenzene), followed by hydroxylation of this alkyl benzene . Together with its positional isomer thymol (2-isopropyl-5-methylphenol), carvacrol is one of the major volatile constituents of essential oils extracted from numerous aromatic plants, , namely, oregano and thyme, and has been reported to display, among others, antioxidant, , analgesic, anti-inflammatory, antinociceptive, antidepressant, anxiolytic, anticarcinogenic, and antimicrobial properties, which have been summarized in various review papers. − Such a wide range of biological properties makes carvacrol a very promising compound to be used in clinical practice. , Moreover, it also finds important applications as an insecticide, a herbicide, and in the cosmetic and food industries as a component to produce fragrances and flavor additives. , …”

Status and Prospects of Botanical Biopesticides in Europe and Mediterranean Countries

“…Carvacrol shows post-emergent effects. It inhibited Amaranthus retroflexus , Avena fatua , Echinochloa crus-galli , Erigeron bonariensis , and Portulaca oleracea [ 48 , 191 ]. Thymus species also show pre-emergent allelopathic performance.…”

“…Many other Thymus species also showed phytotoxic effects to further herbs [ 192 ], indicating that thyme essential oil, in general, has high herbicidal potential and can be used in a wide range of weeds. Thymol and carvacrol were shown to be more phytotoxic than glyphosate, referring to the root growth of Echinochloa crus-galli [ 191 ]. It also acted on some glyphosate-resistant weeds [ 48 ], suggesting that thyme essential oil could be used especially on glyphosate-resistant weeds, e.g., Portulaca oleracea [ 48 ].…”

“…The monoterpenes carvacrol, γ-terpinene, and thymol are known to disrupt the cell membrane and to influence several metabolic pathways, photosynthesis, cell respiration and mitosis [ 171 , 206 ]. However, there is not much known about the exact mechanism of carvacrol in plant metabolism [ 137 ], but it seems that this monoterpene deploys cytotoxic effects [ 191 , 207 ] that harm several plants. Similar to other monoterpenes, carvacrol has intense inhibitory effects on germination and seedling growth [ 179 ], suggesting that pathways other than photosynthesis are induced by carvacrol.…”