Herbicidal cyano-tetrahydrofuranylmethyl ether and cyano-tetrahydropyranylmethyl ether derivatives

A compound of the formula ##STR6## wherein R.sup.1 and R.sup.2 each independently is a hydrogen atom or an alkyl group containing 1 to 6 carbon atoms;

• n is 0 or 1;
• and R is an alkenyl or alkynyl group containing 2 to 4 carbon atoms;
• a 2-pyridinyl group;
• a 2-pyridazinyl group;
• a pyrazinyl group;
• a pyrimidinyl group, a 2-furanyl group;
• or a phenyl group optionally substituted by one or more of halogen, cyano, amino, or an alkoxy or alkylthio group containing 1 to 3 carbon atoms each optionally substituted by one or more halogen atoms having an atomic number of 9 or 17, or by an alkyl group containing 1 or 2 carbon atoms optionally substituted by one or more halogen atoms having an atomic number of 9 or 17, hydroxy or alkoxy or alkylthio containing 1 to 2 carbon atoms.