γ-Lactonizations of 2H-chromenes via cyclopropanation

Stokes, Sean; Spears, Ben; Laseter, Cameron; Barker, Bobby Lloyd; Mead, Keith T.

doi:10.1016/j.tetlet.2010.05.059

Cited by 9 publications

(1 citation statement)

References 20 publications

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“…10 We have previously shown that 2-aryl 2 H -chromenes can be stereoselectively lactonized in a two-step cyclopropanation-rearrangement sequence. 11 Thus, treatment of chromene 8a with the diazo derivative 9a in the presence of catalytic Rh 2 (S-TBSP) 4 gave the donor-acceptor cyclopropane 10 , which rearranged to the α-carbomethoxy lactone 12 on treatment with Sn(OTf) 2 . Originally, we intended to use benzyl protective groups, but unfortunately chromene 8b was unreactive to cyclopropanation.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of 3-benzylidene-dihydrofurochromen-2-ones: promising intermediates for biflavonoid synthesis

Baron

Mead

2015

Heterocyclic Communications

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A route to 3-benzylidene dihydrofurochromen-2-ones from 2H-chromenes is described. Lactonization of 2H-chromenes was achieved using a two-step cyclopropanation-rearrangement sequence. Subsequent conversion of these intermediates to the corresponding α-benzylidene lactones was achieved by lithium enolate Aldol reaction, followed by base-promoted elimination of the aldolate mesylates. The alkene geometry was found to be base-dependent. While KOtBu favored formation of the E-isomer, DBU showed a slight preference for the Z-isomer. In further studies, these 3-benzylidene dihydrofurochromen-2-ones were converted to polyaromatic structures possessing all the required functionality for biflavonoid synthesis.

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Section: Resultsmentioning

confidence: 99%