Synthesis of 2H‐1,4‐Oxazin‐3(4H)‐One Utilizing Umpolung Reaction to α‐Hydrazonoketone

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Abstract 2H‐1,4‐Oxazin‐3(4H)‐One Derivatives Are Known to Exhibit a Wide Range of Biological Activities Such as Antifungal, Anticancer, as Receptor Antagonists and Potassium Channel Modulators. In This Report, We Describe That α‐Hydrazonoketone Is an Appropriate Substrate for the Umpolung Reaction and a Promising Candidate for the Synthesis of 2H‐1,4‐Oxazine‐3(4H)‐Ones. Notably, Umpolung N‐Methylation for α‐Hydrazonoketone Proceeded Quantitatively in a Mild and Extremely Short Reaction Time, Which Has Been Difficult to Achieve in the Conventional Reactions. Moreover, We Also Developed Tandem Umpolung Reaction/Reduction/N‐Acyl‐O‐Alkylation to Afford 2H‐1,4‐Oxazin‐3(4H)‐Ones in High Yield in the Presence of Chloroacetyl Chloride.