add_action( 'woocommerce_before_add_to_cart_button', 'pm_before_add_to_cart_btn' );

function pm_before_add_to_cart_btn(){
	 echo <<<EOL
        <script type="text/javascript">
        jQuery( document ).ready(function($) {
            $('[name="add-to-cart"]').click(function(e){
                e.preventDefault();
                var p_title = $('.product_title').text();
                location.href = "https://api.whatsapp.com/send?phone=12223334444&text=" + p_title;
            });
        });
        </script>
    
    EOL;
}