An efficient and facile electrophilic iodocyclization for the synthesis of various O-, N-, and S-containing dihaloheterocycles has been developed. A wide range of the substituted propargyl alcohols having –OH, –NTs, and –SAc functional groups reacted with molecular iodine or bromoiodine at ambient temperature to produce the corresponding dihalogenated O-, N-, and S-containing five- and six-membered
aryl, and heteroaryl moieties can be prepared in good to excellent yields (up to 99%) by allowing 1,4-butyne-diol, 4-aminobut-2-yn-1-ol, and pent-2-yne-1,5-diol derivatives to react with different electrophiles (I2, IBr, and ICl) at room temperature. Both halogen atoms generated from electrophiles were used effectively. The resulting halides can be further exploited by using palladium-catalyzed coupling
A New Approach to the Synthesis of N-Protected 2- and 5-Substituted 3-Halopyrroles
作者:Thierry Masquelin、Daniel Obrecht
DOI:10.1055/s-1995-3893
日期:1995.3
A new and efficient method for the preparation of N-protected 5- and 2-substituted 3-bromopyrroles 15 and 16 via acid-catalyzed cyclization of the corresponding acetylenic ketones 6 and acetylenic acetals 14 has been found (Scheme 3). Using this methodology, rapid and quite general access to highly substituted pyrroles, which are known to exhibit a number of interesting biological activities, has been established.
Iodine sets allenes ringing: A novel iodine‐promoted tandem cyclization reaction of but‐2‐yne‐1,4‐diol and 4‐aminobut‐2‐yn‐1‐ol derivatives leading to substituted 3,4‐diiodoheterocyclic compounds has been developed (see scheme). In this reaction, a trace amount of water is needed. Both the iodine anion and cation generated from I2 are used in the reaction. The resulting iodides can then be used in
Iron-Catalyzed Cyclization of Alkynols with Diorganyl Diselenides: Synthesis of 2,5-Dihydrofuran, 3,6-Dihydro-2<i>H</i>-pyran, and 2,5-Dihydro-1<i>H</i>-pyrrole Organoselanyl Derivatives
作者:Kamila K. Casola、Davi F. Back、Gilson Zeni
DOI:10.1021/acs.joc.5b01448
日期:2015.8.7
An iron-catalyzed system, using diorganyl diselenides as an organoselenium source, was used for the cyclization of 1,4-butyne-diols in the preparation of 3,4-bis(organoselany1)-2,5-dihydrofurans. The optimized reaction conditions are compatible with many functional groups in 1,4-butyne-diols and diorganyl diselenides. In addition, this catalyst system was also efficient with diorganyl disulfides, but it did not work for diorganyl ditellurides. The same reaction conditions were also extended to pentyne-1,5diol for the preparation of 4,5-bis(organoselany1)-3,6-dihydro-2H-pyrans and to 4-amino-butynol for the preparation of 2,5-dihydro1H-pyrrole derivatives. The synthetic utility of these heterocycles was studied using 5-bis(organoselany1)-3,6-dihydro-2H-pyrans as substrate in a Kumada-type cross-coupling reaction.