Carbazoles exemplify a class of privileged scaffolds and pharmacophores in medicinal chemistry.1 They have also been found in various bioactive molecules and natural products. Furthermore, these compounds exhibit wide applications as photophysical materials, as in organic light-emitting devices.2 On the other hand, cyclopenta[b]indole is another class of indole alkaloids with a structural motif ubiquitous in numerous bioactive natural products as well as therapeutically important agents.3 The wide range of applications makes both these important frameworks attractive synthetic targets, and the continuous development of practically simple, mild, efficient, and selective methodologies is imperative. Propargylic alcohols are known for their utility as valuable building blocks in the generation of molecular scaffolds of varying complexities.4 In this seminar, distinct strategies towards the synthesis of carbazole and cyclopenta[b]indole frameworks, which avail unique reactivity modes of propargylic alcohols and their derivatives, will be discussed in the literature review. Eventually, our design to obtain these indole alkaloids from various indole C-2 tethered pentynols will be presented.



Figure 1. (A) Select examples of biologically active carbazole and cyclopenta[b]indole natural products. (B) Real Money Rummy Proposal.

References: (1) Schmidt, A. W.; Reddy, K. R.; Knölker, H. J. Chem. Rev. 2012, 112, 3193. (2) Lellouche, J. P.; Koner, R. R.; Ghosh, S. Rev. Chem. Eng. 2013, 29, 413. (3) a) Ekebergh, A.; Börje, A.; Mårtensson, J. Org.Lett. 2012, 14, 6274. b) Sings, H.; Singh, S. In The Alkaloids: Chemistry and Biology; Cordell, A., Ed.; Elsevier Science: Amsterdam, NY, 2003; pp 51−163. (4) a) Tsuji, J.; Mandai, T. Angew. Chem., Int. Ed. Engl. 1996, 34, 2589. b) Engel, D. A.; Dudley, G. B. Org. Biomol. Chem. 2009, 7, 4149. c) Chinchilla, R.; Nájera, C. Chem. Soc. Rev. 2011, 40, 5084.