A simple, green and chemoselective method for methoxymethylation and ethoxymethylation of primary and secondary alcohols using a Lewis acidic room temperature ionic liquid, [C₄mim][InCl₄], as catalyst and reaction medium under ambient temperature, microwave and ultrasonic irradiations is reported. In this catalytic system, the corresponding MOM-and EOM-ethers are obtained in excellent yields and in short reaction times. Furthermore, this catalytic system was used for mild and efficient transformations of these protected alcohols to their corresponding acetates and trimethylsilyl ethers under thermal conditions and microwave and ultrasonic irradiations.