16745-79-2Relevant academic research and scientific papers
Transformations of unsaturated acyclic sugars into enantiomerically pure norbornene derivatives
Horton, Derek,Usui, Takayuki
, p. 33 - 49 (2007/10/02)
The C7 acyclic unsaturated-sugar ester 1, derived from L-arabinose, and its enantiomer serve as convenient dieneophiles for chirality transfer for synthesis of optically pure carbocyclic derivatives through cycloaddition reactions.Reaction of 1 with cyclopentadiene may be controlled to give preparative access to the 5,6-disubstituted norbornene adducts 4a, 5a and 7a, according to the conditions used.The distribution of the four possible isomeric products from this cycloaddition was quantitated, and the effect of substitutional variation on the precursor dienophile 1 was also examined.Adducts 4a and 5a were transformed into such substituted carbocycles of known absolute configuration as the methyl esters (11 and 12) of norbornene (bicyclohept-2-ene)-6-carboxylic acid and nortricyclane (tricyclo2,6>heptane)-3-carboxylic acid in optically pure form, specifically through decarbonylation reactions using RhCl(PPh3)3 (Wilkinson's complex) and Cl.The optical purity of 12 was established by the use of a chiral lanthanide shift-reagent.
DIFFERENTIAL BRIDGING IN THE SOLVOLYSIS OF 6- AND 7-SUBSTITUTED 2-EXO- AND 2-ENDO-NORBORNYL p-TOLUENESULFONATES
Flury, Peter,Grob, Cyril A.
, p. 3195 - 3198 (2007/10/02)
The large difference between the reaction constants ρI for the solvolysis of the 6-exo- and 7-anti-substituted norbornyl tosylates 3 and 7, respectively, is further proof for the hypothesis that 2-norbornyl cations are anisotropic with regard to the transmission of polar effects and that through space induction involves graded bridging.
