A flexible route to 1-bromo-2-alkylcyclopropenes

Preparation of poly(p-phenylene vinylene) derivatives by a debromination–chain polymerization–debromination sequence

“…It should also be noted that lower molecular weights and polydispersity are observed in 4 (M n = 10733, M w = 28493, PDI = 2.64) produced at this low temperature than are attained for P1a and P1b at the higher reaction temperatures of the DPD conditions. Because diethylphosphite is well-known to mediate debromination of vicinal dibromides to produce olefins, [18,29,30] it was not surprising that exposure of isolated 4 to additional diethylphosphite and base at 55 °C led to the formation of PPV derivatives just as in the one-pot reaction of 1 with excess diethylphosphite and base. This is an important control, however, to demonstrate that 4 is a viable species on the path from 1 to P1.…”

Eliminations Involving Carbon–Halogen Bonds and Leading to Highly Strained Rings

“…In the first case the deiodination was brought about by the use of zinc and ultrasound 109 * ; however in other cases the use of a dialkyl phosphite and sodium hydride at 20 • C also provides a very mild and efficient method 110 . In the last case, both cis-and trans-diiodides reacted at similar rates, but while the cis-isomer reacted also with the related reagent diethylphosphite and triethylamine to give the cyclopropene in 20 h at 20 • C, the trans-iso-mer remained largely unchanged under these conditions.…”

“…The 1,2-debromination of tri-and tetrahalocyclopropenes may also be carried out using a dialkylphosphite and either sodium hydride or a tertiary amine at ambient temperature 110 :…”

Lewis Acid Catalyzed Cascade Reactions of 1,6‐Diynes and 1,6‐Enynes with Vinylidenecyclopropanes

“…Tables 1-3 and Scheme 2, the X-ray crystal structures of 4 a, 6 a, 8 a and 10 a and the detailed description of experimental procedures naphthalene, indene derivatives and other extended aromatic systems, which are extremely useful benzenoid compounds for biological studies and material applications. [6] The most important methods for these compounds include annulation via Fischer carbene (the Dçtz reaction) [7] and palladium-catalyzed cyclization of alkynes with arylsilyl triflate via highly reactive benzynes (generated in situ). [8] Herein, we wish to report highly efficient Lewis acid catalyzed cascade intermolecular reactions of N-(4-hydroxy-4,4-diarylbut-2-ynyl)-4-methyl-N-prop-2-ynylbenzenesulfonamides or 1,1-diphenyl-4-prop-2-ynyloxybut-2-yn-1-ol (1,6-diynes) 1 and N-allyl-N-(4-hydroxy-4,4-diarylbut-2-ynyl)-4-methylbenzenesulfonamides (1,6-enynes) 2 with VDCPs 3 that selectively produce polycyclic derivatives 4 and 5 as well as isopropylidene-3,3-diarylcyclobut-1-enylmethyl derivatives 6 or 7 in good to high yields under mild conditions; the resulting products depend on the substituents on the benzene rings of 3 along with an interesting PtCl 2 -catalyzed cyclization and a CuA C H T U N G T R E N N U N G (OAc) 2 ·H 2 O catalyzed Eglinton coupling reaction.…”