Microwave-Assisted Three-Component Reaction for Rapid Synthesis of Some 5,6-Dihydro-4H-1,3-thiazine Derivatives Under Solvent-Free Conditions

Abstract

Microwave irradiation was found to efficiently promote the three-component reaction of aromatic aldehyde, thiourea, and vinylbenzene at the presence of TMSCl. The products of 5,6-dihydro-4H-1,3-thiazines were formed in a very short time with good to excellent yields as well as excellent diastereoselectivity. This newly developed protocol provided a much more facile route of preparing functionalized thiazine compounds.

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ACKNOWLEDGMENTS

The authors gratefully acknowledge the financial support from NCET-520 of the National Ministry of Education of China and Natural Science Foundation of Zhejiang Province (Z206510).

Notes

^a 5 mmol aldehyde, 5 mmol styrene, and 6 mmol thiourea in the presence of 7.5 mmol TMSCl at open reflux microwave reactor.

^b 6 mL mixed solvent.

^c Isolated yield.

^d Commercially obtained concentrated hydrochloride acid (37%) was used (7.5 mmol) (based on HCl).

^e 98% H₂SO₄ was used in 5 mmol in 5 mL water.

^a 0.5 mmol aldehyde, 0.5 mmol vinylbenzene, and 0.6 mmol thiourea were mixed and irradiated under 120 W of microwave irradiation for 3 min.

^b Isolated yield.

^c The molecular weight of target products were observed by ESI-MS analysis.

^d The reaction was irradiated for 5 min at 260 W of microwave irradiation.