De-novo approach for a unique spiro skeleton-1,7-dioxa-2,6-dioxospiro[4.4]nonanes

Add time:08/31/2019    Source:sciencedirect.com

2-Oxoglutaric acid (1) underwent facile indium mediated allylation with allyl bromide (2), and ethyl 4-bromocrotonate (3), cinnamyl bromide (4) and subsequent in situ dehydration to provide respective 5-oxotetrahydrofuran-2-carboxylic acids 5–7 (90–95%). The reaction of 1 with 3 and 4 proceeded with high regio and stereo selectivity to provide only γ-addition products with syn stereochemistry as ascertained from their cyclic products. Compounds 5–7 underwent diastereoselective iodocyclization to provide respective 1,7-dioxa-2,6-dioxospiro[4.4]nonanes 8–13. The relative stereochemistries have been ascertained by single crystal X-ray structures, NOE experiments and coupling constants in 1H NMR spectra.

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