Claims:1. A method for synthesizing a Z-9-tetradecenyl acetate, a sex attractant pheromone, comprising the steps of:
a. acetylating 6-bromohexan-1-ol with acetyl chloride in presence of DMAP and toluene to give 6-bromohexyl acetate,
b. reacting oct-3-yn-1-ol with Nickel acetate in presence of EDA, methanol and sodium borohydride to obtain (Z)- oct-3-en-1-ol,
c. chlorinating the (Z)- oct-3-en-1-ol in presence of MDC, TEA using a chlorinating agent to obtain (Z)-1-chlorooct-3-ene, and
d. coupling of 6-bromohexyl acetate and Grignard reagent of (Z)-1-chlorooct-3-ene to obtain Z-9-tetradecenyl acetate.
2. The method for synthesis of Z-9-tetradecenyl acetate as claimed in claim 1, wherein, the 6-bromohexan-1-ol is prepared by bromination of hexane-1,6-diol with HBr in presence of toluene.
3. The method for synthesis of Z-9-tetradecenyl acetate as claimed in claim 1, wherein, the chlorinating agent is selected from thionyl chloride, sulfuryl chloride, either alone or in combination with chlorine.
4. The method for synthesis of Z-9-tetradecenyl acetate as claimed in claim 1, wherein the coupling of 6-bromohexyl acetate and Grignard reagent of (Z)-1-chlorooct-3-ene is carried out in presence of CuI, with THF and MTBE as a solvent to obtain Z-9-tetradecenyl acetate.
5. The method for synthesis of Z-9-tetradecenyl acetate as claimed in claim 1, wherein a sex attractant pheromone is a Z-9-tetradecenyl acetate, is sex attractant insect pheromone preferably of fall armyworm.
, Description:Technical Field of the Invention
The present invention relates to a method for synthesizing Z-9-tetradecenyl acetate, which is a sex attractant, insect pheromone preferably of fall armyworm.

Background of the Invention
Insect pheromones can be used in a variety of insect control strategies that include mating disruption and attract-and-kill, as well as mass trapping. These strategies have proven to be effective, selective (e.g., they do not harm beneficial insects, such as bees and lady bugs), and safe (e.g., the pheromone compounds are generally biodegradable and do not accumulate in the food chain). Even the very stringent USDA Organic Program lists insect pheromones as one of the few synthetic organic compounds allowed in organic crop production, another important recognition of the high safety of these products. Accordingly, pheromones already form the basis of integrated pest management (IPM) practices in fruit production on the U. S. west coast, and their use in organic farming is growing worldwide.
Even though thousands of insect pheromones have been identified, less than about twenty insect pests worldwide are currently controlled using the pheromone strategies, and only 0.05% of global agricultural land employs pheromones.

As is well known, extermination of various kinds of noxious insects not only in household but also agriculture and forestry is carried out less and less by use of chlorine-containing or phosphorus-containing organic chemicals which may cause serious environmental pollution or a health problem in human body. Instead, one of the promising chemical means for the extermination of noxious insects is the use of the so-called sexual pheromones. A sexual pheromone is a secretion of the insect of a sex and attracts the insects of the other sex of the same species even in an extremely small amount.
Several of the sexual pheromones have already been investigated chemically in detail and their chemical structures have been established. Examples of them are: cis-7-dodecenyl acetate; cis-9-tetradecenyl acetate; cis-11-hexadecenyl acetate; cis-11-hexadecenol; cis-11-hexadecenal; and cis-3-cis-13-octadecadienyl acetate and their use for the extermination of the respective noxious insects is now on the way of development.

Insect pests destroy crops and/or spread disease. Common peps: control methods involve spraying farmland, orchards, wetlands, forests, or other pest habitats with insecticides. This method is problematic because insecticides are applied directly to crops or watersheds, and this practice is contrary to an increasing preference for organic produce as well as contrary to water quality issues and other environmental concerns. Insecticides are also non-discriminate killers and kill beneficial insects as well as harmful insects. Finally, the insect pests are becoming increasingly resistant to many of the common insecticides.

An alternative method to control insect populations involves the use of the insect's sex attractant to confuse the male insect and thereby prevent mating and eliminate future insect generations. This technique is called mating pane disruption. Insect pheromones constitute a relatively new class of compounds that have a number of advantages over conventional insecticides. Insect pheromones are nontoxic and environmentally friendly. They are specific to the target insect and do not adversely affect beneficial insects and, they have not been shown to induce the development of resistance in the target insects. The biggest drawbacks in using mating pattern disruption to control insect populations is the cost of producing the insect pheromone, which is typically far more expensive than that of traditional insecticides. Methods that reduce the production costs of insect pheromones would make mating pattern disruption an economical technique for controlling insect populations and thereby minimize environmental concerns associated with pest control.
A new and practical synthesis of (Z)-9-tetradecen-1-yl acetate using 1,8-octane-diol was reported by Lucia Gansca et al, published in in Revista de Chimie -Bucharest- Original Edition- 62(9):878-880· September 2011. The route involves use of the mercury derivative of the terminal alkyne ?-functionalised as intermediate, which is lithiated and then alkylated. The first coupling reaction took place between monosodium acetylene obtained in situ and 1-tert-butoxy-8-bromo-octane. The second coupling reaction consisted in directly lithiated of di(tert-butoxy-dec-9-yne)mercury and then alkylated with 1-bromo-butane obtaining 1-tert-butoxy-tetradec-9-yne. After acetylation and stereoselective reduction in the presence of NiP-2 catalyst of 1-tert-butoxy-tetradec-9-yne gave (Z)-tetradecen-1-yl acetate. This process has drawbacks of using mercury derivative and lithiated compounds which are highly toxic and hence not feasible to practice on industrial level. Moreover, if these impurities remain in the final product, the passing of these heavy metals into the food chain cannot be ruled out.

These compounds can be prepared with an economically advantageous using safer raw materials methods for the synthetic preparation of them have not yet been proposed.
Therefore, there remains a need in the art to provide an economically feasible and industrially scalable method for the production of Z-9-tetradecenyl acetate, a sex attractant, insect pheromone preferably of fall armyworm.

Brief Summary of the Invention
It is an object to develop an economically feasible method for the synthetic preparation of the above named sexual pheromone compounds, viz., Z-9-tetradecenyl acetate and, in the course of the’ investigations, arrived at a discovery of a compound which is useful as an intermediate for the synthesis of the sexual pheromone compounds.

The above-named sexual pheromone can be synthesized economically in high yields, i.e., Z-9-tetradecenyl acetate.

Brief Description of the Drawings
The present invention will be more readily understood from the detailed description of embodiments thereof made in conjunction with the accompanying drawings of which:

Fig. 1 – is a step wise synthetic scheme of preparation of Z-9-tetradecenyl acetate.

Detailed Description of the invention
The main object of the present invention is to provide a novel process for preparation of a sex attractant the Fall armyworm pheromone, namely Z-9-tetradecenyl acetate using 6-bromohexyl acetate wherein the process comprises the following steps:
a. acetylating 6-bromohexan-1-ol with acetyl chloride in presence of DMAP and toluene to give 6-bromohexyl acetate,
b. reduction of oct-3-yn-1-ol with Nickel acetate in presence of sodium borohydride and Ethylenediamine (EDA) to obtain (Z)- oct-3-en-1-ol,
c. chlorinating the (Z)- oct-3-en-1-ol using chlorinating agent in presence of MDC, TEA , to obtain (Z)-1-chlorooct-3-ene, and
d. coupling of 6-bromohexyl acetate with Grignard reagent of (Z)-1-chlorooct-3-ene to give Z-9-tetradecenyl acetate.

In an embodiment, the invention provides a process for preparation of starting material, 6-bromohexyl acetate wherein the process comprises bromination of hexane-1,6-diol with HBr in presence of toluene to obtain 6-bromohexan-1-ol and acetylating the 6-bromohexan-1-ol with acetyl chloride in presence of N,N-Dimethyl amino pyridine (DMAP) and toluene to yield 6-bromohexyl acetate.

In an embodiment, the chlorinating agent is selected from thionyl chloride, sulfuryl chloride, either alone or in combination with chlorine.
In another embodiment, the invention provides a process for preparation of Z-9-tetradecenyl acetate which process involves the coupling of 6-bromohexyl acetate and Grignard reagent of (Z)-1-chlorooct-3-ene in the presence of copper iodide in THF & MTBE as a solvent system to give Z-9-tetradecenyl acetate.
In yet another embodiment, the invention provides a process for preparation of Grignard reagent of (Z)-1-chlorooct-3-ene which process comprises reacting (Z)-1-chlorooct-3-ene with Magnesium turnings in THF in presence of Iodine and 1,2-dibromoethane under reflux.

The process of the present invention results in Z-9-tetradecenyl acetate with an yield of 59% and with a purity of 95.0 %.
The present invention provides synthesis of olefinic alcohols, acetates, or derivatives thereof in an economical and efficient manner. Most of these reactions are run neat, and the unreacted starting materials are recycled back into the next reactions.

The method for synthesis of (Z)-9-tetradecenyl acetate according to the invention presents an advantageous pathway with high isomeric purity. The key step is the coupling of bromo derivative i.e., 6-bromohexyl acetate with Grignard reagent of (Z)-1-chloro oct-3-ene in THF using CuI, to obtain (Z)-9-tetradecenyl acetate.

Scheme 1: illustrates the synthesis of (Z)-9-tetradecenyl acetate

Experimental details:
Example 1. Synthesis of 6-bromohexyl acetate:
Charged Toluene (1.0 Lt) and 1,6-Hexanediol (100 g) at 25-30°C, stirred, and slow addition of HBr (100 ml) and raised the temperature to reflux then cooled the reaction mixture, separated both aqueous and organic layers and distilled off the organic layer under vacuum to yield 6-Bromo hexanol, which is further charged with MDC (500 ml) followed by DMAP (6.8 g), cooled to 0°C under stirring, followed by slow addition of acetyl chloride (48 g), under stirring, separated both aqueous and organic layers, washed the MDC layer with Brine solution dried the MDC layer over anhydrous Na2SO4 and filtered, and distilled the MDC layer under vacuum, to yield 6-Bromo hexyl acetate (100 gm), analyzed by GC, with an yield of 53.0 % and Purity of 95.0 %.
Example 2. Synthesis of 1-chloro-3Z-Octene:
Charged methanol (500 ml) under N2 atmosphere at 25-30 °C and charged nickel acetate (40 g), stirred, and further added sodium borohydride (7.3 g) portion wise followed by slow addition of ethylenediamine (24 g), stirred and added 3-octyn-1-ol (100 g) and simultaneously passed hydrogen, filtered and distilled off methanol under vacuum, cooled, add HCl (20 ml), and charged MDC (400 ml), stirred and separated aqueous and organic layers followed by washing of MDC layer with water to obtain MDC layer with 3Z-Octene-1-ol. This was cooled 10 °C, added TEA (94 g), stirred, followed by addition of thionyl chloride (120 g), stired, and separated aqueous and organic layers, washed MDC layer with sodium bicarbonate solution (30 g in 300 ml water), dried with sodium sulphate (20 g), and distilled of MDC under vacuum to yield 1-Chloro-3Z-Octene (90 g), analyzed by GC, with an yield of 80 % and Purity of 95.0 %.

Example 3. Synthesis of (Z)-9-tetradecenyl acetate:
Charged Magnesium turnings (18 g) under nitrogen atmosphere and added THF (150 ml ) slowly into the RBF at 65°C under nitrogen atmosphere, and charged Iodine, 1,2-dibromoethane (0.2 ml) and 1-chloro-3Z-octene (100 g) in THF (250 ml), stirred under reflux, cooled the Grignard reagent to 30°C. Charged THF (240 ml). In another RBF , added 6- bromo hexyl acetate (120 g) and Copper iodide (4.1 g) at 5°C and added Grignard reagent of 1-chloro-3Z-octene, stirred and quenched with ammonium chloride solution (200 ml), separated both aqueous and organic layers, charged MTBE (200 ml) to the aqueous layer for extraction, washed the combined MTBE and THF layers with brine solution, distilled off organic layer under vacuum to get (Z)-9-tetradecenyl acetate (80gr), analyzed by GC, with an yield of > 59 % and Purity of >95.0 %.