Microwave-assisted reactions of α-diazoketones with hetaryl and ferrocenyl thioketones^*

* Dedicated to Professor Zbigniew Kudzin (University of Łódź) on the occasion of his 70th birthday.

ABSTRACT

Differently substituted hetaryl thioketones react with less reactive diazoketones under microwave (MW) irradiation in toluene solution. After only 2 min, the reactions were complete and, depending on the type of the used diazoketone, α,β-unsaturated ketones, acyl substituted thiiranes or 1,3-oxathioles were obtained as final products. In the case of azibenzil and di(thiophen-2-yl) thioketone, a new type of 1,5-dipolar electrocyclization of the intermediate thiocarbonyl ylide involving a thiophene ring led to a fused sulfur heterocycle. In contrast to hetaryl thioketones, the ferrocenyl analogues decompose under MW irradiation. Alternatively, they react with diazopropanone and 2-diazo-1-phenylethanone in boiling THF in the presence of LiClO₄ to give α,β-unsaturated ketones as sole products. In these cases, the reactions require long reaction times.

GRAPHICAL ABSTRACT

KEYWORDS:

• Diazo compounds
• thioketones
• microwave irradiation
• thiocarbonyl ylides
• sulfur heterocycles

Acknowledgements

Skillful performance of elemental analysis of all new compounds by Ms Agnieszka Cieślińska and Ms Hanna Jatczak (University of Łódź) is gratefully acknowledged. The authors thank also Ms Małgorzata Celeda for her help in preparation of diverse starting materials explored in this study.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

* Dedicated to Professor Zbigniew Kudzin (University of Łódź) on the occasion of his 70th birthday.

Additional information

Funding

The authors thank the National Science Center (Cracow, Poland) for generous financial support (Grant Maestro-3 (Dec-2012/06/A/ST5/00219)).