Synthetic access to 6,7-dihydro-4H-pyrazolo[5,1-c][1,4]oxazines has been achieved in 3–4 steps from commercially available pyrazoles. Optimization of a protected hydroxyethyl group on N1 enabled the regiocontrolled construction of pyrazole-5-aldehydes in high yields; subsequent deprotection and reduction generated fused heterocyclic scaffolds bearing multiple substitution patterns. Moreover, the intermediate pyrazole lactols were shown to be versatile synthetic building blocks.

中文翻译：

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区域控制合成6,7-二氢-4H-吡唑并[5,1-c] [1,4]恶嗪

从市售吡唑分3至4步即可合成6,7-二氢-4 H-吡唑并[5,1- c ] [1,4]恶嗪。N1上受保护的羟乙基的优化使得能够高产地控制吡唑-5-醛的区域控制；随后的脱保护和还原生成带有多个取代模式的稠合杂环支架。此外，中间体吡唑乳醇被证明是通用的合成构件。