| 摘要 |
<p>Chromogenic fluorene-9-spiro-lactones have the formula: <CHEM> where R1, R2, R3, R4 and E have defined meaning. The compounds can be made by diazotizing and then effecting a ring closing reaction on the corresponding precursor primary amino-substituted phthalide, furopyridine or furopyrazine. Compounds where E is a group of the formula <CHEM> and R1, R2, R3, R4, R5 and R6 are each C1-C4 alkyl groups are preferred. The compounds are chromogenic and can be used in pressure and/or heat sensitive record material. They give light-fast blue to green colours when reacted with electron accepting co-reactants. The coloured forms exhibit marked absorption in the near infrared making them particularly useful in OCR detection systems.</p> |
