Over the past decade, the most significant, conceptual advances in the field of fluorination were enabled most prominently by organo- and transition-metal catalysis. The most challenging transformation remains the formation of the parent C-F bond, primarily as a consequence of the high hydration energy of fluoride, strong metal-fluorine bonds, and highly polarized bonds to fluorine. Most fluorination reactions still lack generality, predictability, and cost-efficiency. Despite all current limitations, modern fluorination methods have made fluorinated molecules more readily available than ever before and have begun to have an impact on research areas that do not require large amounts of material, such as drug discovery and positron emission tomography. This Review gives a brief summary of conventional fluorination reactions, including those reactions that introduce fluorinated functional groups, and focuses on modern developments in the field.

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Introduction of Fluorine and Fluorine-Containing Functional Groups

Metal-catalyzed carbon-sulfur bond formation.

In recent years, the use of essential oils (EOs) derived from aromatic plants as low-risk insecticides has increased considerably owing to their popularity with organic growers and environmentally conscious consumers. EOs are easily produced by steam distillation of plant material and contain many volatile, low-molecular-weight terpenes and phenolics. The major plant families from which EOs are extracted include Myrtaceae, Lauraceae, Lamiaceae, and Asteraceae. EOs have repellent, insecticidal, and growth-reducing effects on a variety of insects. They have been used effectively to control preharvest and postharvest phytophagous insects and as insect repellents for biting flies and for home and garden insects. The compounds exert their activities on insects through neurotoxic effects involving several mechanisms, notably through GABA, octopamine synapses, and the inhibition of acetylcholinesterase. With a few exceptions, their mammalian toxicity is low and environmental persistence is short. Registration has been the main bottleneck in putting new products on the market, but more EOs have been approved for use in the United States than elsewhere owing to reduced-risk processes for these materials.

Essential oils in insect control: low-risk products in a high-stakes world.

https://chemistry.mdma.ch/hiveboard/rhodium/pdf/piper.phytochemistry.pdf

Phytochemistry of the genus Piper

The long term use of many insecticides is continually threatened by the ability of insects to evolve resistance mechanisms that render the chemicals ineffective. Such resistance poses a serious threat to insect pest control both in the UK and worldwide. Resistance may result from either an increase in the ability of the insect to detoxify the insecticide or by changes in the target protein with which the insecticide interacts. DDT, the pyrethrins and the synthetic pyrethroids (the latter currently accounting for around 17% of the world insecticide market), act on the voltage-gated sodium channel proteins found in insect nerve cell membranes. The correct functioning of these channels is essential for normal transmission of nerve impulses and this process is disrupted by binding of the insecticides, leading to paralysis and eventual death. Some insect pest populations have evolved modifications of the sodium channel protein which prevent the binding of the insecticide and result in the insect developing resistance. Here we review some of the work (done at Rothamsted Research and elsewhere) that has led to the identification of specific residues on the sodium channel that may constitute the DDT and pyrethroid binding sites.

https://iubmb.onlinelibrary.wiley.com/doi/epdf/10.1080/15216540701352042

DDT, pyrethrins, pyrethroids and insect sodium channels.

(1979). The Piperaceae Amides I: Structure of Pipercide, A New Insecticidal Amide from Piper nigrum L. Agricultural and Biological Chemistry: Vol. 43, No. 7, pp. 1609-1611.

https://www.jstage.jst.go.jp/article/bbb1961/43/7/43_7_1609/_pdf

The Piperaceae Amides I: Structure of Pipercide, A New Insecticidal Amide from Piper nigrum L.

Firstly, major physico-chemical impacts resulting from the incorporation of fluorine atom into hydrocarbon moiety of organic molecules are briefly described in alternate reference to its unique electronic features and various physical parameters essential with recent structure-activity studies, some of which are discussed respectively as active examples of pesticide developments on the basis of quantitative structure-activity relationship. Then, a number of new or important fluorine chemistry are introduced as useful tool for synthesis of pesticide molecules having fluorine atom. Finally, 24 of selected examples of fluorine containing pesticides of mostly late issue are compiled in view of visualizing the recent R & D trend.

https://www.jstage.jst.go.jp/article/yukigoseikyokaishi1943/42/9/42_9_809/_pdf

Recent Trend in New Pesticides Containing Fluorine

Although structure modifications of natural pyrethrin constituents have disclosed a variety of potent synthetic analogues, all known examples are cyclopropanecarboxylate esters, a grouping that appeared to be essential for insecticidal activity Some new substituted 2-phenylalkanoates, whose biological activities are of a similar nature and potency to those of conventional pyrethroids, are now reported 5-Benzyl-3-furylmethyl and 3-phenoxybenzyl 3-methyl-2-phenylbutyrates and their analogues are potent insecticides Activity is increased on the introduction of appropriate groups into the 3 and/or 4-positions of the aryl ring and the (S)-2-phenylalkanoates are far more active than their (R)-enantiomorphs Structure/activity relationships are compared with those for conventional pyrethroids Some of the new series compare favourably with typical insecticides in tests against Musca domestica, Spodoptera litura and Plutella xylostella

2-arylalkanoates, a new group of synthetic pyrethroid esters not containing cyclopropanecarboxylates†

(1974). A New Class of Pyrethroidal Insecticides; α-Substituted Phenylacetic Acid Esters. Agricultural and Biological Chemistry: Vol. 38, No. 4, pp. 881-883.

Hirosuke Yoshioka

Papers

The Piperaceae Amides I: Structure of Pipercide, A New Insecticidal Amide from Piper nigrum L.

Recent Trend in New Pesticides Containing Fluorine

2-arylalkanoates, a new group of synthetic pyrethroid esters not containing cyclopropanecarboxylates†

A New Class of Pyrethroidal Insecticides; α-Substituted Phenylacetic Acid Esters

Highly selective ring opening of epoxides with silicon tetrafluoride: Preparation of fluorohydrins