Cascade and Effective Syntheses of Functionalized Tellurophenes
摘要:
A one-pot and transition-metal-catalyst-free synthetic strategy to construct functionalized tellurophenes has been developed. Substituted 1,1-dibromo-l-en-3-ynes are smoothly converted to tellurophenes with telluride salts in high yield via a series of cascade reactions through reductive debromination, hydrotelluration, nucleophilic cyclization, and aromatization. Close inspection of the results clearly showed that the reactivity of in situ prepared telluride salts are significantly influenced by the polarity of the solvent system and the electronic nature of the substituent on the enyne substrate. This method reports the first direct synthesis of 3-aryltellurophenes in high yields at room temperature. This novel reaction strategy is also found to be a promising synthetic method for multisubstituted tellurophenes and selenophenes.
An efficient enantioselectiveorganocatalytic method for the synthesis of N-alkylated indoles with α-branched alkyl substituents from the corresponding unsaturated indolyl ketones via a Michaeladdition has been developed. The resulting products were obtained in high enantioselectivities and in good yields. Various nucleophiles (nitroalkanes, malononitrile, malonic esters) can be used. The substitution
Synthesis of Unsymmetrically Substituted 1,3-Butadiynes and 1,3,5-Hexatriynes via Alkylidene Carbenoid Rearrangements
作者:Annabelle L. K. Shi Shun、Erin T. Chernick、Sara Eisler、Rik R. Tykwinski
DOI:10.1021/jo026481h
日期:2003.2.1
Unsymmetrically substituted 1,3-butadiynes and 1,3,5-hexatriynes are synthesized in four steps from commercially available aldehydes or carboxylic acids. The key step in this process involves a Fritsch-Buttenberg-Wiechell rearrangement, in which an alkylidene carbenoid intermediate subsequently rearranges to the desired polyyne. This rearrangement proceeds under mild conditions, and it is tolerant
Bestmann–Ohira reagent. The reaction offers a convenientroute for the synthesis of regioisomerically pure 3,5-disubstituted or 3,4,5-trisubstituted pyrazoles in excellent yields. However, di-ynones and molecules possessing both ynone and enone functionalities provide only monocycloaddition products, whereas another multiple bond undergoes Michaeladdition with the methoxide anion.
A supported palladium nanocatalyst for copper free acyl Sonogashira reactions: One-pot multicomponent synthesis of N-containing heterocycles
作者:Subhankar Santra、Kalyan Dhara、Priyadarshi Ranjan、Parthasarathi Bera、Jyotirmayee Dash、Swadhin K. Mandal
DOI:10.1039/c1gc15869d
日期:——
efficient heterogeneous nanocatalytic system for the copper free acyl Sonogashirareaction. A wide range of ynones was synthesized in high yields undermildreactionconditions. The catalyst was recovered and recycled up to four times. Transmission electron microscopy (TEM) images revealed that the catalyst maintained nanospheric dimensions for four consecutive catalytic cycles. This simple protocol was further
β-Silyl-Assisted Tandem Diels–Alder/Nazarov Reaction of 1-Aryl-3-(trimethylsilyl) Ynones
作者:Rachael A. Carmichael、Punyanuch Sophanpanichkul、Wesley A. Chalifoux
DOI:10.1021/acs.orglett.7b00911
日期:2017.5.19
A one-pot tandem Diels–Alder/Nazarov reaction of 1-aryl-3-(trimethylsilyl) ynones has been achieved to generate carbo- and heterocyclic fused ring systems in good to excellent yields. The β-silyl effect is instrumental in accessing this otherwise challenging cascade annulation reaction. The tandem reaction proceeds in the presence of BCl3 to generate three new carbon–carbon bonds, a quaternary carbon