A new approach was developed to synthesize 1,4-oxazine and 1,4-oxazepine derivatives without solvent and metal. Regioselective cyclization occurred to afford exclusively the exo-dig product, and stereochemistry was studied by circular dichroism and specific optical rotation techniques. The Grignard reaction is a key synthetic step to produce high diastereomeric compounds via Cram's rule and was well supported by DFT calculations. A hydroalkoxylation mechanism was proposed and supported by DFT calculations.