Unusual Transformation of Cyclobutenediones into Butenolides

Abstract

Butenolides are prepared from cyclobutenediones when cyclobutenediones are treated with lithium trimethylsilylacetylene, and quenched with water. A plausible mechanism, which contains an allene as an intermediate, is proposed. The usual diradical intermediate may not be formed because of the bulkiness of trimethylsilyl group, and the allenic intermediate may be stabilized by the α-silyl group.

Synthesis of chiral hexynones for use as precursors to native photosynthetic hydroporphyrins

“…The transformation relied on access to one-carbon stannane synthons, which can undergo lithium-tin transmetalation 52,53 at low temperature (≤−78 °C) to afford the corresponding in situ generated α-oxygenated organolithium nucleophiles. Compounds Sn-Me , 54 Sn-MOM , 55 Sn-THP , 56 Sn-MEM , 57 Sn-Bn , 58 and Sn-SEM 59 were prepared according to literature procedures from tributyltin hydride via tributyl(iodomethyl)tin or tributyl(hydroxymethyl)tin 60 and characterized by 1 H and 13 C{ 1 H} NMR spectroscopy; the syntheses are listed here for completeness. Chromatographic purification of compound 53 Sn-(OMe) 2 resulted in a significant loss of the product (although the 1 H and 13 C{ 1 H} NMR spectra still matched the literature data 53 ).…”

“…Known compounds Sn-(OMe) 2 , 53 Sn-Me , 54 Sn-MOM , 55 Sn-THP , 56 Sn-MEM , 57 Sn-Bn , 58 and Sn-SEM 59 were prepared as described in the literature. Known compounds 18–23 and IV-b were prepared herein in streamlined syntheses and/or in larger scales than reported previously.…”