Three-component reactions with (S)-methyl pyroglutamate: an efficient way to diversely substituted asymmetric amidocyclohexenes.

ABSTRACT

Chiral N-dienyl lactams are crucial building blocks for the synthesis of complex organic compounds. However, their generation is rather challenging. This paper reports the novel one-pot reaction of (S)-methyl pyroglutamate as the amide component with different aldehydes and dienophiles (AAD reaction) to give novel chiral 1-amido-2-cyclohexenes. The corresponding N-dienyl lactams generated in situ undergo subsequent Diels-Alder reactions in good yield and diastereoselectivity. The scope and limitations of the three-component protocol were investigated. X-ray and NMR spectroscopic analysis of the products as well as DFT calculations of the intermediates were also performed to explain the observed stereoselectivity and structural features.