Fukuyama indole synthesis  The Fukuyama indole synthesis is a versatile tin mediated chemical reaction that results in the formation of 2,3-disubstituted indoles. A practical one-pot reaction that can be useful for the creation of disubstituted indoles. Most commonly tributyltin hydride is utilized as the reducing agent, with azobisisobutyronitrile (AIBN) as a radical initiator. Triethylborane can also be used as a radical initiator. The reaction can begin with either an "ortho"-isocyanostyrene or a 2-alkenylthioanilide derivative, both forming the indole through Radical cyclization "via" an α-stannoimidoyl radical. The R group can be a range of both basic and acidic sensitive functional groups such as esters, THP ethers, and β-lactams. In addition the reaction is not stereospecific, in that both the "cis" and "trans" isoform can be used to obtain the desired product. The reaction mechanism begins with the creation of the tributyl tin radical with either AIBN or triethylborane, not shown in either step-wise mechanism. Following the radical attacks the o-isocyano carbon creating the alpha-stannoimidoyl radical. Through radical cyclization a five membered ring is formed followed by the propagation of a new tin radical. The final step is dependent on the desired outcome of the reaction. This reaction is a one-pot synthesis and results in yields ranging from 50% to 98% depending on the substituent. The mechanism using 2-alkenylthioanilide is very similar, also starting with the formation of a bond, now between the tin radical and the sulfur. Followed by a similar radical cyclization resulting in a five membered ring, a new tin radical is produced and the original attacking radical leaves with the sulfur substituent. This part of the step-wise mechanism has yet to be detailed. The reaction yield can range from 40% to 93% depending also on the desired substituent. The Fukuyama Indole synthesis can generate a range of different substituents at the 2,3 position that were previously unattainable without a protecting group on the nitrogen in the ring. One such example is the 2-iodoindole derivative, which can then lead to a variety of N-unprotected 2,3 substituted indoles.