112423-38-8Relevant academic research and scientific papers
On the stereoselectivity of γ-lactol substitutions with allyl- and propargylsilanes - Synthesis of disubstituted tetrahydrofuran derivatives
Schmitt, Andreas,Reissig, Hans-Ulrich
, p. 3893 - 3901 (2000)
Monosubstituted γ-lactols 1a-1c, 3a-3c and 4a-4c, as well as disubstituted γ-lactol 5 and the γ-hydroxy-substituted γ-lactone 6, were transformed into disubstituted tetrahydrofuran derivatives by treatment with allyl- and propargylsilanes in the presence of Lewis acids. The diastereoselectivities were moderate to excellent and are interpreted by application of the Felkin-Anh model to cyclic oxocarbenium ions. The effects of the equilibria between conformers of the intermediates are discussed. The surprisingly high diastereoselectivity of 4-substituted γ-lactols 3 can be explained on this basis.
A Chelate-Controlled Route to Disubstituted and Tetrasubstituted γ-Lactones Stereoselectivity in Lewis Acid Promoted Additions to Chiral Methyl β-Formylcarboxylates
Kunz, Thomas,Janowitz, Agnes,Reissig, Hans-Ulrich
, p. 2165 - 2176 (2007/10/02)
On reaction with allyltrimethylsilane/TiCl4, chiral methyl β-formylcarboxylates 1a - 1h provide disubstituted and tertasubstituted γ-lactones 3a - 3h with moderate to excellent diastereoselectivities.Other Lewis acids are less selective.The formation of seven-membered ring chelates 1.TiCl4 has been proven unambiguously by NMR spectroscopy in several cases.Trichloromethyltitanium displays a selectivity pattern similar to the reagent combination allylsilane/TiCl4.Aldehydes 1a - 1d, 1g, and 1h give primarily trans-γ-lactones, whereas under appropriate conditions 1f affords an excess of cis-γ-lactone 3f.These results are discussed with regard to the Felkin-Anh model and to chelate formation.Model studies with simpler chiral aldehydes 5 and 7 as well as with acetals 9a/b and 11a/b are presented and discussed.They emphasize the importance of chelate control in additions to β-formyl esters 1. - Key Words: γ-Lactones, di- and tetrasubstituted / Chelates, seven-membered / Allylsilane additions, Lewis acid promoted / Felkin-Anh model / Aldehydes, chiral
Radical Additions in Aqueous Medium: Direct Synthesis of 5-Allyl-Substituted γ-Lactones from Allylic Bromides/Zinc and Methyl γ-Oxocarboxylates
Kunz, Thomas,Reissig, Hans-Ulrich
, p. 891 - 894 (2007/10/02)
Following a procedure published by Luche, 5-allyl-substituted γ-lactones 2a - 2d are prepared in good yield from methyl γ-oxocarboxylates 1a - 1c and allyl bromides/zinc dust in aqueous medium.The diastereoselectivity of this allylation reaction is compared to that of Lewis acid promoted additions of allyltrimethylsilane to chiral aldehydes. - γ-Lactones; Radical additions; Felkin-Anh model
