Beilstein J. Org. Chem.2022,18, 1256–1263, doi:10.3762/bjoc.18.131
approaches were contemplated for this purpose. Activation by alkoxides of the C3–SiEt3 or C3–SiMe2t-Bu bonds was ineffective. Conversely, treatment of the C3-benzyldimethylsilyl-appended derivatives with tetrabutylammonium fluoride led to cyclicsiloxanes, which revealed to be competent donors for copper
carbinols from renewable feedstock.
Keywords: biomass; copper; cyclicsiloxanes; 2-furyl carbinols; silicon; Introduction
Progress towards the use of nonedible renewable feedstock to replace fossil resources as starting material for high-value chemicals is an important endeavor of modern synthesis [1][2
to form pentavalent silicon intermediates F. Instead, the reason was probably a too low intrinsic stability of the C3-lithiated furans G, which thwarted 1,4-silyl migration. Conversely, this experiment provided evidence that cyclicsiloxanes (e.g., 16), which are potential nucleophilic partners for
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Graphical Abstract
Scheme 1:
C3–Si bond functionalization of biomass-derived 3-silylated furfural platforms.
Beilstein J. Org. Chem.2017,13, 2122–2127, doi:10.3762/bjoc.13.209
] and oxasilacycloalkenes (cyclicsiloxanes, cf. Figure 1) [6][7][8] is an excellent method to prepare stereodefined alkenes. The cyclicsiloxanes can be prepared in a number of ways: hydrosilylation of alkynes [11][12][13], semihydrogenation of silyl alkynes [14], ring-closing metathesis (RCM) [15][16
][17][18][19][20][21] and enyne metathesis [22][23].
We became interested in the cross-coupling of cyclicsiloxanes in the context of preparing trisubstituted Z-styrenes for the synthesis of natural product targets [24]. Heliannuol A was the first member of a family of allelopathic [25][26][27
of helianane.
Conclusion
In summary, we have confirmed the Hiyama cross-coupling of cyclicsiloxanes is an efficient route to Z-trisubstituted styrenes that are useful for the synthesis of natural product frameworks. Although yields are low under the conditions attempted, a proof of concept has been
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Graphical Abstract
Figure 1:
Retrosynthetic analysis of heliannuol A.