Facile synthesis of spiro-pyrazolone-tetrahydrofurans/pyrans: ipso-cyclization of arylidene pyrazolones with haloalcohols

A new method to generate a series of spiro-pyrazolone-tetrahydrofurans/pyrans is developed by using a base-mediated cascade ipso-cyclization of unsaturated pyrazolones and haloalcohols. Noteworthy aspects of this methodology include its brief reaction duration, expansive substrate applicability, very good yields, and mild reaction conditions without the need for transition metals. Interestingly, the practical feasibility of the present strategy is also investigated in gram scales that provided good yields of the products.