58564-80-0Relevant academic research and scientific papers
On the effect of tether composition on cisltrans selectivity in intramolecular diels-alder reactions
Paddon-Row, Michael N.,Longshaw, Alistair I.,Willis, Anthony C.,Sherburn, Michael S.
, p. 126 - 134 (2009)
Intramolecular Diels-Alder (IMDA) transition structures (TSs) and energies have been computed at the B3LYP/6-31+G(d) and CBS-QB3 levels of theory for a series of 1,3,8-nonatrienes, H2C=CH-CH=CH-CH2X-Z-CH= CH2 [-X-Z-=-CH2-CH2(1); -O-C(=O)- (2); -CH 2-C(=O)-(3); -O-CH2- (4); -NH-C(=O)- (5); -S-C(=O)- (6); -O-C(=S)- (7); -NH-C(=S)- (8); -S-C(=S)- (9)]. For each system studied (1-9), cis- and trans-TS isomers, corresponding, respectively, to endo- and exo-positioning of the -C-X-Z- tether with respect to the diene, have been located and their relative energies (ErelTS) employed to predict the cis/trans IMDA product ratio. Although the Erel TS values are modest (typically -1), they follow a clear and systematic trend. Specifically, as the electronegativity of the tether group X is reduced (X=O-→ NH or S), the IMDA cis stereoselectivity diminishes. The predicted stereochemical reaction preferences are explained in terms of two opposing effects operating in the cis-TS, namely (1) unfavorable torsional (eclipsing) strain about the C4-C5 bond, that is caused by the -C-X-Q=Y)- group's strong tendency to maintain local planarity; and (2) attractive electrostatic and secondary orbital interactions between the ertdo(thio)carbonyl group, C=Y, and the diene. The former interaction predominates when X is weakly electronegative (X=N, S), while the latter is dominant when X is more strongly electronegative (X=O), or a methylene group (X=CH2) which increases tether flexibility. These predictions hold up to experimental scrutiny, with synthetic IMDA reactions of 1, 2, 3, and 4 (published work) and 5, 6, and 8 (this work) delivering ratios close to those calculated. The reactions of thiolacrylate 5 and thioamide 8 represent the first examples of IMDA reactions with tethers of these types. Our results point to strategies for designing tethers, which lead to improved cis/trans-selectivities in IMDAs that are normally only weakly selective. Experimental verification of the validity of this claim comes in the form of fumaramide 14, which undergoes a more trans-selective IMDA reaction than the corresponding ester tethered precursor 13.
Rapid photoassisted access to N,O,S-polyheterocycles with benzoazocine and hydroquinoline cores: Intramolecular cycloadditions of photogenerated azaxylylenes
Mukhina, Olga A.,Bhuvan Kumar,Arisco, Teresa M.,Valiulin, Roman A.,Metzel, Greg A.,Kutateladze, Andrei G.
supporting information; experimental part, p. 9423 - 9428 (2011/11/06)
Ring the changes: A new photoassisted approach to give conformationally constrained N,O,S-polyheterocyclic scaffolds of unprecedented topologies was achieved by intramolecular [4+4] and [4+2] cycloadditions of photogenerated o-azaxylylenes (23 examples; see scheme). The precursors can be readily assembled by simple and high-yielding reactions, thus making this a powerful synthetic method amenable to high-throughput diversity-oriented synthesis.
Total synthesis of epoxyquinols A, B, and C and epoxytwinol A and the reactivity of a 2H-pyran derivative as the diene component in the Diels-Alder reaction
Shoji, Mitsuru,Imai, Hiroki,Mukaida, Makoto,Sakai, Ken,Kakeya, Hideaki,Osada, Hiroyuki,Hayashi, Yujiro
, p. 79 - 91 (2007/10/03)
(Chemical Equation Presented). Full details of two versions of the total synthesis of epoxyquinols A, B, and C and epoxytwinol A (RKB-3564D) are described. In the first-generation synthesis, the HfCL4-mediated diastereoselective Diels-Alder rea
Endo selective Diels-Alder reactions of furan in ionic liquids
Hemeon, Ivan,DeAmicis, Carolyn,Jenkins, Hilary,Scammells, Peter,Singer, Robert D.
, p. 1815 - 1818 (2007/10/03)
Diels-Alder reactions of the heteroaromatic diene furan proceed with enhanced isolated yields and reversal of endolexo selectivity (2:1 endo vs exo) in the ionic liquids [bmim]BF4 and [bmim]PF6 compared to conventional methods. The p
