99249-28-2Relevant articles and documents
DIASTEREOSELECTIVE CYCLOPROPANATION VIA HOMOCHIRAL KETALS. DIOXOLANE STRUCTURAL EFFECTS
Mash, Eugene A.,Nelson, Keith A.,Heidt, Philip C.
, p. 1865 - 1868 (2007/10/02)
A series of 2-cyclohexen-1-one ketals related to 2-cyclohexen-1-one 1,4-di-O-benzyl-L-threitol ketal but possessing different dioxolane appendages was prepared and subjected to Simmons-Smith cyclopropanation.The observed diastereoselectivity decreased when oxygen was present in the appendages.In the absence of appendage oxygen, the sense of the observed diastereoselectivity was found to depend upon dioxolane chirality.The amount of diastereoselectivity observed was remarkably independent of the nature of the appendages.
HOMOCHIRAL KETALS IN ORGANIC SYNTHESIS. DIASTEREOSELECTIVE CYCLOPROPANATION OF α,β-UNSATURATED KETALS DERIVED FROM 1,4-Di-O-BENZYL-L-THREITOL
Mash, Eugene A.,Nelson, Keith A.
, p. 679 - 692 (2007/10/02)
2-Cykloalken-1-one 1,4-di-O-benzyl-L-threitol ketals undergo efficient and diastereoselective cyclopropanation when treated with an excess of the Simmons-Smith reagent.For example, 2-cyclohexen-1-one 1,4-di-O-benzyl-L-threitol ketal gave in 90-98percent yield a 9:1 mixture of diastereomeric cyclopropanes as established by 62.9 MHz 13C NMR spectroscopy and by hydrolysis of the mixture to (1R,6S)-bicycloheptan-2-one.Sixteen other examples are presented which demonstrate the generality and predictability of the process for 2-cycloalken-1-one ketals, as well as an unfortunate lack of diastereoselectivity for α,β-unsaturated 1,4-di-O-benzyl-L-threitol acetals.
