36872-10-3Relevant academic research and scientific papers
A Bio-Inspired, Catalytic e → Z Isomerization of Activated Olefins
Metternich, Jan B.,Gilmour, Ryan
, p. 11254 - 11257 (2015/09/21)
Herein, Natures flavin-mediated activation of complex (poly)enes has been translated to a small molecule paradigm culminating in a highly (Z)-selective, catalytic isomerization of activated olefins using (-)-riboflavin (up to 99:1 Z/E). In contrast to the prominent Z → E isomerization of the natural system, it was possible to invert the directionality of the isomerization (E → Z) by simultaneously truncating the retinal scaffold, and introducing a third olefin substituent to augment A1,3-strain upon isomerization. Consequently, conjugation is reduced in the product chromophore leading to a substrate/product combination with discrete photophysical signatures. The operationally simple isomerization protocol has been applied to a variety of enone-derived substrates and showcased in the preparation of the medically relevant 4-substituted coumarin scaffold. A correlation of sensitizer triplet energy (ET) and reaction efficiency, together with the study of additive effects and mechanistic probes, is consistent with a triplet energy transfer mechanism.
An SN2′ displacement approach to allenyl acetates
Asikainen, Martta,Lewis, William,Blake, Alexander J.,Woodward, Simon
supporting information; experimental part, p. 6454 - 6456 (2011/01/03)
Reaction of cuprates derived from R3MgBr/CuI/LiBr (R3 = n-alkyl) with R1CCCH(O2CR2)2 (R1 = sp2 hybridised substituent, R2 = mainly Me, alkyl, Ph) provides access to allenyl esters R1R 3CCCH(O2CR2) (51-88%). Such species are not accessible via rearrangement of precursor propargylic R1R 3C(O2CR2)CCH.
Regiospecific and Stereospecific Synthesis of E- and Z-Trisubstituted Alkenes via 2,2-Disubstituted Vinylsilanes
Chou, Shang-Shing P.,Kuo, Hwei-Lon,Wang, Chung-Jen,Tsai, Chung-Ying,Sun, Chung-Ming
, p. 868 - 872 (2007/10/02)
Treatment of terminal alkynes 1 with the organocopper reagents derived from Grignard reagents, cuprous iodide, and lithium bromide (molar ratio 2:1:2) at low temperature followed by the addition of chlorotrimethylsilane gave the 2,2-disubstituted vinylsilanes 2 with complete regio- and stereospecificity (syn addition).Electrophilic substitution of 2 with ICl, Br2, and acetyl chloride gave the corresponding vinyl iodides, bromides, and α,β-unsaturated ketones 5 with retention of configuration.Epoxidation of 2 with MCPBA gave the epoxy silanes 6, which upon treatment with concentrated HX and BF3*Et2O gave the vinyl halides 7 with net inversion of configuration.If the epoxy silanes 6 were first converted to the β-hydroxy silanes 8 by Gilman's reagents, either E- or Z-trisubstituted alkenes 9 and 10 could be obtained by treatment with acid or base.Vinyl halides 7 could also be stereoselectively converted to other functionalities via the vinyllithium intermediates.
ALKENYL COPPER REAGENTS-18; CARBOCUPRATION OF ACETYLENIC ACETALS AND KETALS; SYNTHESIS OF MANICONE, GERANIAL AND 2,4(E,Z)-DIENALS
Alexakis, A.,Commercon, A,Coulentianos, C.,Normant, J.F.
, p. 715 - 732 (2007/10/02)
Lithium diorganocuprates add across the triple bond of substituted and non-substituted acetylenyl acetals and ketals to give dialkenylcuprates, which can be decomposed into alkoxyallenes or may be trapped with a variety of electrophiles, such as alkyl, alkenyl, alkynyl and aryl halides.They may also undergo conjugate addition to α-β unsaturated esters and ketons.The method is used for the synthesis of (+/-)-manicone, pure geranial and (E,Z)2,4-dienals.
