appconfigconfig.yml
...
doctrine:
    dbal:
        default_connection: default
        connections:
            default:
                driver:   pdo_mysql
                host:     "%database_host%"
                port:     "%database_port%"
                dbname:   "%database_name%"
                user:     "%database_user%"
                password: "%database_password%"
                charset:  UTF8
            dinamica:
                driver:   pdo_mysql
                host:     "%database_host%"
                port:     "%database_port%"
                dbname:   ~
                user:     "%database_user%"
                password: "%database_password%"
                charset:  UTF8
    orm:
        default_entity_manager: default
        entity_managers:
            default:
                connection: default
                mappings:
                    AppBundle:  ~
                auto_mapping: true
            dinamica:
                connection: dinamica
                mappings:
                    AppBundle:  ~

/*AppBundleEventListenerApplicationConnector.php*/
<?php

/*Asigna la bd a la conexion dinamica.*/

namespace AppBundleEventListener;

use SymfonyComponentDependencyInjectionContainerAwareInterface;
use SymfonyComponentDependencyInjectionContainerInterface;
use SymfonyComponentHttpKernelExceptionNotFoundHttpException;
use DoctrineDBALConnection;

class ApplicationConnector implements ContainerAwareInterface
{

    /**
     * @param SymfonyComponentDependencyInjectionContainerInterface $container
     */
    public function setContainer(ContainerInterface $container = NULL)
    {
        $this->container = $container;
    }
    /**
     * @param $sucursal
     */
    public function getBDDinamica($sucursal)
    {
        $em = $this->container->get('doctrine')->getManager();
        $bancoselect = $em->getRepository('AppBundle:Sucursal')->findOneBy(array('sucursal' => $sucursal));
        $dbalServiceName = sprintf('doctrine.dbal.%s_connection', 'dinamica');
        //Obtiene la conexcion dinamica
        $dynamicCon = $this->container->get($dbalServiceName);
        $refCon = new ReflectionObject($dynamicCon);
        $refParams = $refCon->getProperty('_params');
        $refParams->setAccessible('public');
        $params = $refParams->getValue($dynamicCon);
        $params['dbname'] = $bancoselect->getDbname();
        $params['user'] = $bancoselect->getDbuser();
        $params['password'] = $bancoselect->getDbpassword();
        $refParams->setValue($dynamicCon,$params);
        $refParams->setAccessible('private');

        return $dynamicCon;
    }
}