1334723-29-3Relevant academic research and scientific papers
Frustrated lewis pair reactions with bis-acetylenic substrates: Exploring the narrow gap separating very different competing reaction pathways
Liedtke, Rene,Froehlich, Roland,Kehr, Gerald,Erker, Gerhard
, p. 5222 - 5232 (2011)
Tris(pentafluorophenyl)borane reacts with 9,9-dipropargylfluorene (5) in a 2:1 ratio under ambient conditions to yield a statistical mixture of the double-1,1-carboboration products (Z,Z)-, (E,Z)-, and (E,E)-6. Photolysis of the product mixture yields a new mixture that is substantially enriched in the (Z,Z)-6 isomer. Treatment of 5 with the P(o-tolyl)3/B(C 6F5)3 frustrated Lewis pair gave the zwitterionic eight-membered heterocycle 7a, which is the product of a 1,1-carboboration of one alkynyl unit followed by an intramolecular 1,2-addition of the in situ generated new FLP to the remaining alkynyl moiety. The reaction of the PtBu3/B(C6F5)3 FLP gave an analogous result, yielding 7b. Treatment of 1,2-diethynylbenzene (9) with the PtBu3/B(C6F5)3 FLP resulted in deprotonation, forming the phosphonium/alkynylborate salt 10. The reaction of triarylphosphine/B(C6F5)3 pairs using the phosphines P(o-tolyl)3 and P{Ph2[2,5- bis(trifluoromethyl)phenyl]} resulted in clean 1,2-P/B FLP additions to a C≡C triple bond to yield the products 11 and 12, respectively. Eventually, the reaction of 9 with the poorly nucleophilic phosphine P(C6F 5)3 in combination with B(C6F5) 3 gave the zwitterionic product 14, which is thought to result from a two-step reaction involving 1,1-carboboration followed by an exo-dig cyclization by means of a 1,2-P/B FLP reaction of the in situ generated alkenylborane Lewis acid and P(C6F5)3 to the remaining alkynyl unit. The products (Z,Z)-6, 7a,b, 10, 12, and 14 were characterized by X-ray crystal structure analyses.
