of α-keto- or α- formyl acetals by Witting reaction with cyclopropylidenetriphenyl-phosphorane leads to α cyclopropylidene-acetals, easily deacetalized by moist silicagel into the corresponding α-cyclopropylidene-ketone and α-cyclopropylidene-aldehydes. The conversion of the latter to the former is also easily carried out by reaction with Grignardreagents followed by oxidation with active manganese
Cleavage of Isoxazolines with Tricarbonyltris(acetonitrile)molybdenum and Silica Gel. Synthesis of 1-(2-Oxoalkyl)cyclopropanols from lsoxazoline-5-spirocyclopropanes
作者:Antonio Guarna、Antonio Guidi、Andrea Goti、Alberto Brandi、Francesco De Sarlo
DOI:10.1055/s-1989-27185
日期:——
An efficient synthesis of 1-(2-oxoalkyl)cyclopropanols [or (1-hydroxycyclopropyl)methyl ketones] from isoxazoline-5-spirocyclopropanes by selective N-O cleavage effected by Mo(CO)3(MeCN)3 and silica gel is described.
Previous transition metal-catalyzed synthesis processes of δ-diketones are plagued by the high cost of the rhodium catalyst and harsh reaction conditions. Herein a low-cost, roomtemperature ruthenium catalytic method is developed based on the coupling of α-keto sulfoxoniumylides with cyclopropanols. The mild protocol features a broad substrate scope (47 examples) and a high product yield (up to 99%)
α-cyclopropylidene carbinols (the 1,2-addition product). Addition of methyl-lithium and lithium dimethylcuprate lead to the expected 1,2- and 1,4-additionproducts, respectively. The comparison of these results and those corresponding to α-isopropylidene-ketones confirms the higher tendency of α-cyclopropylidene-ketones to give 1,4-additionproducts; the measurement of polarographic reduction potentials confirms