A Tandem, Bicatalytic Continuous Flow Cyclopropanation-Homo-Nazarov-Type Cyclization

作者：Aponte Guzman Joel; Shenje Raynold; Huang Yong; Woodham Wesley H; Saunders Steven R; Mostaghimi Sina M; Flack Kyle R; Pollet Pamela^*; Eckert Charles A; Liotta Charles L; France Stefan

来源：Industrial & Engineering Chemistry Research, 2015, 54(39): 9550-9558.

DOI：10.1021/acs.iecr.5b02715

Continuous flow processing represents an emerging technology in the chemical and pharmaceutical industries. Herein, we describe a tandem, bicatalytic continuous flow cyclopropanation-homo-Nazarov-type ring-opening cyclization to form hydropyrido[1,2-a]indoles, which represents a naturally occurring chemical scaffold present in many bioactive and therapeutically relevant molecules. The tandem flow reactions provided high conversions (>97%) with product throughputs on the order of 3-5 g h(-1). The individual transformations (cyclopropanation and ring-opening cyclization) were separately optimized in the batch then successfully transferred to the flow. Significantly, this represents the first literature example of continuous flow cydopropane ring-opening cydizations; hydropyrido[1,2-a]indoles are formed on a multigram scale (>4 g h(-1) throughput) in near-quantitative yields from N-indolyl-1,1-cyclopropyl beta-amidoesters. Overall, the continuous flow technology exhibited superior yields, relative to the batch reactions, for both the ring-opening cyclizations and the tandem, bicatalytic reactions. These results provide the basis for large-scale implementation of bicatalytic cyclopropanation-ring-opening cyclization reactions for complex synthesis and represent initial efforts toward the development of an industrially viable, four-step continuous flow synthesis of hydropyrido [1,2-a]indoles.

• 出版日期2015-10-7