Herein, we describe a gold(I)-catalyzed generation of nonclassical gold-containing 1,4-all-carbon dipoles from cycloisomerization/1,2carbene transfer/ring opening cascade reactions of readily accessible allenyl ketones bearing a cyclopropyl moiety and its cyclization with tropone. This method features an unprecedented formal [8+4] high-order cycloaddition under mild conditions for delivering structurally complex 7,7,5-tricycles in generally moderate to high yields.
The inherently strained furan-fused
cyclobutenes, in situ generated via cycloisomerizations
of allenyl ketones bearing cyclopropyl
moiety under gold catalysis, have been utilized as reactive building
blocks toward cross cycloadditions. The [4 + 2] and [3 + 2] annulations
of these species with benzo[c]isoxazoles and N-iminoquinazolinium ylides furnish various three-dimensional
cyclobutane-bridged polyheterocycles in good yields. A wide range
of typically electron-deficient 1,3-dienes, heterodienes, and 1,3-dipoles
can trap furan-fused cyclobutenes to afford several polycyclic architectures.
The in situ formed furan-fused cyclobutenes via Cu(I)-catalyzed cycloisomerization of readily available allenyl ketones bearing a cyclopropyl moiety are a highly reactive and powerful species, which undergo annulative fragmentation with terminal ynones to afford a wide variety of functional furans in moderate to high yields. This ring-distortion protocol features an unprecedented strain-controlled cycloisomerization/Diels−Alder/retro-Diels−Alder (CDRD) sequence under mild conditions.involving furan-fused cyclobutenes to create structurally new molecules are currently being pursued in our laboratory.
■ ASSOCIATED CONTENT
* sı Supporting InformationThe Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.orglett.2c00578.Experimental procedures and copies of 1 H and 13 C NMR spectra for all new compounds; crystallographic data for compounds 3a-tosylhydrazone and 3abtosylhydrazone (PDF)Accession Codes CCDC 2150987−2150988 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk
The metal-free cyclization of allenyl ketones and ptoluenesulfonylmethyl isocyanide (TosMIC), promoted by Cs 2 CO 3 , provides a convenient access to tetrasubstituted pyrroles in which an acyl group undergoes 1,2-migration. This tandem Michael addition/annulative migration synthetic strategy is general and high-yielding for various substituted allenyl ketones. Moreover, a phosphoryl or ester moiety is also a suitable functionality to enable such migration. Note pubs.acs.org/joc
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