Process for preparing substituted cyclopropycarbinyl compounds

#This invention relates to novel cyclopropyl compounds having biological activity, especially pesticidal and anti-inflammatory activity, and to a method of controlling weeds, insects, bacteria, fungi and other plant and animal pests using certain of these compounds.

#A variety of compounds are currently used for the control of insect and plant pests. Included among such pesticidal compounds are chlorinated hydrocarbons, arsenic compounds, mercury compounds and the like. While effective for their intended use, the safety of such materials is currently under question largely because of their poor biodegradability and high mammalian toxicity. Current trends in the chemical control of insect and plant pests call for inherently safer materials which degrade very rapidly to non-toxic substances once their purpose is accomplished. Accordingly, there is great demand for alternative broad spectrum pesticides which are suitable for the high volume usage entailed in agricultural applications.

#Of the several types of biodegradable insecticides currently available, those compounds containing a cyclopropyl moiety, e.g., the derivatives of chrysanthemic acid, are of high potential utility inasmuch as these compounds have a relatively low initial mammalian toxicity and biodegrade under field conditions to non-toxic products. However, it has long been recognized that the preparation of compounds containing the cyclopropyl moiety is difficult inasmuch as this 3-membered ring is quite strained and is not readily established by ordinary chemical means. To date, compounds containing the cyclopropyl or cyclopropylcarbinyl group have had to be prepared by such methods as the zinc dust condensation of 1,3 -dihalides, a method which yields only small amounts of the desired cyclopropyl derivatives because of intermolecular coupling reactions. The addition of ##STR1## fragments to olefins has also been employed, but requires expensive reactants. Accordingly, improved methods for preparing compounds containing the cyclopropyl moiety would be highly desirable, inasmuch as an economical route to such compounds would provide the basic intermediates for the preparation of a variety of biologically active cyclopropyl derivatives.

#In a 100 ml. 3-necked flask under argon atmosphere were admixed 6.9 g. of 3-butenyltributyltin and 25 ml. of methylene chloride (solvent). 1 ml. of bromine (electrophile source) was added to the solution of the 3-butenyltin compound in dropwise fashion. The reaction was exothermic. The reaction mixture was cooled slightly with a cold water bath until completion. The reaction mixture was transferred to a 100 ml. flask and concentrated on a rotary evaporator with gentle warming. The mixture was distilled at atmospheric pressure to yield a fraction boiling at about 103.degree. C-108.degree. C. This fraction was shown by proton nmr to be cyclopropylcarbinyl bromide. Yields were on the order of 80%.

#6.9 g. of 3-butenyltributyltin was dissolved in 20 ml. of dry CH.sub.2 Cl.sub.2 in a 50 ml. flask under an argon atmosphere. The flask was equipped with a rubber injection septum and a dry ice-acetone slush condenser. The reaction vessel was immersed in a cooling bath filled with a dry ice-acetone slush (-70.degree. C). The chlorine gas was slowly bubbled through the solution. The reaction was checked for disappearance of 3-butenyltributyltin by gas chromatography. Once g.l.c. analysis indicated that all 3-butenyltributyltin had disappeared, the reaction mixture was transferred to a flask and distilled at atmospheric pressure. The final portion was removed with aspirator vacuum and slight heating. The first cut of the distillate was analyzed by proton nmr and proved to be cyclopropylcarbinyl chloride.

#In the above procedure, the 3-butenyltributyltin is replaced by an equivalent amount of 3-butenyltriethyltin and 3-butenyltripentyltin, respectively, and equivalent results are secured. In the above procedure, the 3-butenyltributyltin is replaced by an equivalent amount of tetrakis-(3-butenyl)tin and chlorine gas is introduced into the reaction mixture for a period of time approximately 4-fold that when 3-butenyltributyltin is employed in the process and cyclopropylcarbinyl chloride is secured.