Metal free, one pot 1,6-Conjugate Addition of Diol on para-Quinone Methide followed by ipso cyclization: An Approach to Spiro 1,4-Dioxane cyclohexadienone Derivatives.

A novel one-pot transition metal-free and Brönsted acid mediated 1,6-conjugate addition of bisnuleophilic diol on biselectrophilc para-quinone methide followed by ipso cyclization assisted by NBS has been developed under mild reaction conditions, offers a new approach to synthesize spiro 1,4-dioxane cyclohexadienone derivatives. This strategy features broad substrate scope of p-QMs with high functional group tolerance and good yields of spirocyclic scaffolds (60-92 %). N-Bromo succinimide an important role in an ipso spirocyclization with high efficiency.