An I2O5/KSCN-Mediated Iodothiocyanation of Alkynes
Thiocyanates are an important compound family that widely found in natural products and active pharmaceutical ingredients.In addition,their ability to function as versatile electrophiles either on sulfur or carbon centers enables them especially valuable intermediates in synthetic organic chemistry.In the past decades,considerable advances for synthesis of thiocyanates have been made.However,most of them rely on transition-metal promotion or suffer from harsh reaction conditions or limited substrate scope.Therefore,efficient and practical accesses to thiocyanates are highly desirable.Herein,we disclose herein a general and practical access to(E)-β-iodo vinylthiocyanates via iodothiocyanation of alkynes with I2O5 and KSCN.In contrast to previous methods,the present strategy holds the advantages of transition-metal free,high diaster-oselectivity,scaled-up to grams and mild conditions.By treatment of the alkynes with I2O5 and KSCN at room temperature,we found that a wide variety of terminal and/or internal alkynes all gave the corresponding(E)-β-iodo vinylthiocyanates in high yields and excellent chemoselectivities.In addition,the desired(E)-β-iodo vinylthiocyanates were also obtained in good yields with both aryl and simple alkyl substituted alkynes.Interestingly,propargyl alcohol was also effective substrate.Fur-thermore,several propionates afforded the corresponding(E)-β-iodo vinylthiocyanates as a mixture of regio-isomers.Treat-ment of a herbicide clodinafop-propargyl with I2O5 and KSCN resulted in high yield of the corresponding(E)-β-iodo vinyl-thiocyanates,which indicated that this strategy could be applied in direct modification of drugs.Finally,this iodothiocya-nation reaction can be smoothly scaled-up to gram level,which indicates it could be applied in industrial synthesis of phar-maceuticals.
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