Alkoxycarbonylbenzyltrialkylphosphonium salts

#This invention relates to a novel class of ortho or meta-alkoxycarbonylbenzyltrialkylphosphonium salts and to a method for regulating the natural growth or development of plants using said class of phosphonium compounds. The compounds of this invention are plant regulators which are defined by Congress in Public Law 92-516, the Federal Environmental Pesticide Control Act of 1972, section 2, subsection v, as any substance or mixture of substances intended through physiological action, for accelerating or retarding the rate of growth or rate of maturation, or for otherwise altering the behavior of plants or the produce thereof, but shall not include substances to the extent that they are intended as plant nutrients, trace elements, nutritional chemicals, plant inoculants, and soil amendments. In view of the ever increasing demand for plant products due to the rapid expansion of the world population, considerable research has been conducted to find chemical substances which can be beneficially utilized as plant regulators, such as, agents which retard vegetative growth or are useful for optimizing the yeilds of various crops.

#Various phosphonium compounds are known. For example, U.S. Pat. No. 2,703,814 is directed to the preparation of phosphonium bromides and chlorides. U.S. Pat. No. 3,230,069 and U.S. Pat. No. 3,268,323 are directed to classes of phosphonium compounds useful for the regulation of plant growth. Another class of phosphonium compounds is described in U.S. Pat. No. 3,281,365, useful in antiseptic detergent compositions. A further class of phosphonium compounds useful for controlling nematodes is shown in U.S. Pat. No. 3,642,989.

#This invention is directed to novel class of substituted benzyltrialkylphosphonium salts characterized by having a alkoxycarbonyl substituent in the ortho or meta position of the benzyl ring. This novel class of chemical compounds is represented as follows: ##STR1## wherein R is alkyl of not more than four carbon atoms and is, for example, methyl, ethyl, propyl, isopropyl, butyl, sec-butyl or tert-butyl; wherein R' is alkyl of not more than four carbon atoms and is preferably propyl or butyl and most preferably butyl; and wherein X is Cl, Br, I, SO.sub.4, CO.sub.3, NO.sub.3, or PO.sub.4 and is preferably Br.

#A solution of 22.9 g (0.10 mol) of methyl m-(bromomethyl) benzoate and about 20.2 g (0.10 mol) of tri-n-butylphosphine in 150 ml of benzene in a suitable vessel is stirred at reflux for about 17 hours. The solution is cooled and 250 ml of ether is slowly added along with seed crystals. The resultant solid is collected and washed with ether to yield about 37.9 g (88%) of m-methoxycarbonylbenzyltributylphosphonium bromide, a white solid having a melting point of 144-146.degree., and having a structure in accordance with formula (1) which is confirmed by nuclear magnetic resonance (nmr).

#Anal. Calcd. for C.sub.21 H.sub.36 BrO.sub.2 P: C, 58.47; H, 8.41; Found: C, 58.22; H, 8.38.

#A mixture of 1 g of benzoyl peroxide, 178 g (1.0 mol) of N-bromosuccinimide, and 153 g (0.99 mol) of m-toluoyl chloride in 1400 ml of benzene in a suitable vessel is stirred at reflux using an infrared heat lamp for 2.3 hours. An nmr spectrum shows the reaction mixture to consist of 23% m-toluoyl chloride, 65% .alpha.-bromo-m-toluoyl chloride and 12% .alpha., .alpha.-dibromo-m-toluoyl chloride. The mixture is concentrated under vacuum to about 300 ml, is filtered to remove succinimide, and is further concentrated at 90.degree. (0.6 mm) for several minutes to give 214.8 g of a magenta liquid that contains about 16.5% m-toluoyl chloride, 69% .alpha.-bromo-m-toluoyl chloride, and 14.5% .alpha., .alpha.-dibromo-m-toluoyl chloride.