Combining Silver Catalysis and Organocatalysis: A Sequential Michael Addition/Hydroalkoxylation One-Pot Approach to Annulated Coumarins
摘要:
A highly stereoselective one-pot procedure for the synthesis of five-membered annulated hydroxycoumarins has been developed. By merging primary amine catalysis with silver catalysis, a series of functionalized coumarin derivatives were obtained in good yields (up to 91%) and good to excellent enantioselectivities (up to 99% ee) via a Michael addition/hydroalkoxylation reaction. Depending on the substituents on the enynone, the synthesis of annulated six-membered rings is also feasible.
enones present as s-trans conformers to provide good yields of the silyl enol ethers of beta-acetylido carbonyl compounds. Typically good substrates are 2-cyclopentenone, 2-cyclohexenone, alpha,beta-unsaturatedaldehydes, and beta-alkoxy-alpha-enones. Copper acetylide reagents prepared from CuI and an alkynyllithium give considerably higher yields than those prepared from CuBr or CuCN. Iodotrimethylsilane
Relay Catalysis To Synthesize β-Substituted Enones: Organocatalytic Substitution of Vinylogous Esters and Amides with Organoboronates
作者:Sasha Sundstrom、Thien S. Nguyen、Jeremy A. May
DOI:10.1021/acs.orglett.9b04584
日期:2020.2.21
Organocatalysis was shown to facilitate conjugate additions to vinylogousesters and amides for the first time. Subsequent elimination of a β-alcohol or amine provided π-conjugated β-substituted enones. Remarkably, nucleophile addition to the electron-rich vinylogous substrates is more rapid than classical enones, forming monosubstituted products. A doubly organocatalytic (organic diol and methyl aniline)
A convenient method for the preparation of α-vinylfurans by phosphine-initiated reactions of various substituted enynes bearing a carbonyl group with aldehydes
at the ene end in the presence of various aldehydes, in moderate to high yields. The reaction may consist of 1,6-addition of phosphine to the enynes, ring closure, and Wittig reaction between the ylid resulting from cyclization and an aldehyde. Thus, various aldehydes were able to be used in the reaction. The reaction was influenced greatly by the substituents at the acetylene position (R1) and the α-position
Construction of β to carbonyl stereogenic centres by asymmetric 1,4-addition of alkylzirconocenes to dienones and ynenones
作者:Zhenbo Gao、Stephen P. Fletcher
DOI:10.1039/c8cc01201f
日期:——
A new asymmetric addition of alkylzirconium species to dienones, a dienthioate, ynenones, and ynethionates with good yields and excellent ee's is reported.
The asymmetrichydrogenation of 2,4-pentadien-1-ones has been achieved by using trans-RuCl2[(R)-XylylSunPhos][(R)-Daipen] as a catalyst under basic conditions. This hydrogenation demonstrated exclusive C1-carbonyl selectivity, and thus the conjugated 2,4-diene motifs remained untouched, which provides a synthetically useful method for various chiral 2,4-pentadien-1-ols.