278596-35-3Relevant academic research and scientific papers
Organotransition-metal-modified sugars Part 17. Glucal-derived carbene complexes: syhthesis and diastereoselective benzannulation
Doetz, Karl Heinz,Otto, Frank,Nieger, Martin
, p. 77 - 88 (2001)
The addition of triisopropylsilyl and/or isopropylidene-protected 1-lithio-D-glucals prepared in situ from stannylated precursors 5 and 6 to hexacarbonyl chromium followed by methylation affords D-arabino-hex-1-enopyranosylcarbene complexes 7 and 8. They undergo a diastereoselective benzannulation upon reaction with tolan and 3-hexyne to give polyoxygenated chromans 9 to 12 in good yields and moderate diastereomeric excess values. The confirmation of the glucal moiety in the carbene ligand and in the chroman skeleton is controlled by the nature of the protective groups. 1H-NMR studies and single crystal X-ray analyses indicate a 5H4-conformation of the sugar moiety for the triisopropylsilyl compounds 7, 9a,b, 10a,b and 11 and 4H5-conformation for the isopropylidene derivatives 8 and 12a-c in solution, and further for 8 and 12a in the solid state.
From glycals to metal pyranosylidenes: Diastereoselective addition of electrophiles to metal carbene enolate intermediates
J?kel, Christoph,D?tz, Karl Heinz
, p. 2167 - 2173 (2007/10/03)
Lithiated glucals react smoothly with Cr(CO)5THF at the metal center to generate the corresponding vinyl chromate intermediates which represent chromium carbene enolate equivalents. Trapping by electrophiles provides an entry to novel chromium
