Douglas P. Kjell

Preparation of 2-Aminopyridoimidazoles and 2-Aminobenzimidazoles via Phosphorus Oxychloride-Mediated Cyclization of Aminoureas

The novel preparation of 2-aminopyridoimidazoles and 2-aminobenzimidazoles via the cyclization of (2-aminopyridin-3-yl)urea and (2-aminophenyl)urea substrates in the presence of phosphorus oxychloride is described. This methodology is demonstrated for a range of urea substrates with aminoimidazole products obtained in good yields and with excellent levels of purity.

Origins of Regioselectivity in the Fischer Indole Synthesis of a Selective Androgen Receptor Modulator

The selective androgen receptor modulator, (S)-(7-cyano-4-(pyridin-2-ylmethyl)-1,2,3,4-tetrahydrocyclopenta[b]indol-2-yl)carbamic acid isopropyl ester, LY2452473, is a promising treatment of side effects of prostate cancer therapies. An acid-catalyzed Fischer indolization is a central step in its synthesis. The reaction leads to only one of the two possible indole regioisomers, along with minor decomposition products. Computations show that the formation of the observed indole is most favored energetically, while the potential pathway to the minor isomer leads instead to decomposition products. The disfavored [3,3]-sigmatropic rearrangement, which would produce the unobserved indole product, is destabilized by the electron-withdrawing phthalimide substituent. The most favored [3,3]-sigmatropic rearrangement transition state is bimodal, leading to two reaction intermediates from one transition state, which is confirmed by molecular dynamics simulations. Both intermediates can lead to the observed indole product, albeit through different mechanisms.