Studies On The Addition Reactions Of Functionalization Allenes

Allenes are a class of compounds containing the unique cumulative diene structural units with high reactivity. Great efforts have already been made on the activation of functionalized allenes with Lewis acids followed by attack of different types of nucleophiles. Based on these studies, this dissertation focuses on addition reactions of functionalized allenes, including electrophilic addition of1,2-allenylic sulfoxides and transition metal-catalyzed or proton-promoted hydroarylation or hydroalkylation of2,3-allenoates and3,4-allenoates through attack of carbon nucleophiles. Besides, some intitial studies on addition of C=O double bonds has also been conducted.Part I:Electrophilic addition of1,2-allenylic sulfoxides with H+electrophileOn the basis of previous reports of our group on electrophilic additions of allenes, we have demonstrated two types of such transformations in which the H+served as the electrophile. The first one is the a highly regio-and stereoselective hydration of1,2-allenylic sulfoxide to afford3-sulfinyl-2(Z)-alkenols. Through the X-ray diffraction study, it was concluded that the reaction may proceed via a5-membered cyclic intermediate following by attack of the-OH coming from the solvent at the sulfur atom. Unexpectly, the reaction of1,2-allenylic sulfoxides with HOAc in the precense of H2O2afforded oxidative hydroacetoxylation products3-sulfonylallylic acetates. The axial chirality can be transferred into the center chirality through attack of "OAc at the carbon atom of cyclic intermediate which is different from what was observed in previous halohydroxylation reaction.Part â…¡:Hydroarylation of electron-rich arenes or heterocycles with allenoatesA palladium-catalyzed highly selective allylation of1,3,5-trimethoxybenzene, anisole, and phenol in TFA under mild conditions with2,3-allenoate affording (E)-4,4-diarylbut-2-enoate in40-70%yields was decribed. The coordination of carboxyl group with Pd explains the high stereoselectivity. 4-Indolyl-4-arylbut-2-enoates were obtained through the TFA-promoted regioselective hydroaylation reaction of N-Ts or N-Ac-indoles with2,3-allenoates. The E/Z selectivity was found to depend on the reaction temperature and time. A mechanism involving the formation of E and Z allylic carbocations generated in situ from the reaction of2,3-allenoates with TFA and subsequent Friedel-Carfts attack at the3-position of indole was proposed. N-Ts pyrroles were also tolerated in this reactions.When3,4-allenoates were used, double-hydroarylation reaction occurred with2-and3-position of indole moiety being functionalized in one step to construct a five-membered ring.Part â…¢:Hydroalkylation of1,3-diketones with allenoatesUnder the catalysis of palladium, the relative electron-rich C=C bonds of2,3-allenoates were attacked to afford2(E)-5,5-diacyl-2-alkyl-4-arylhex-2-enoates exclusively with LB-Phos as the ligand representing the first highly selective palladium-catalyzed hydroallylation reaction of2,3-allenoates with1,3-diketones.We explored the double-hydroalkylation of1,3-diketones with3,4-allenoates to prepare ethyl2,2-diacyl-3,3-dialkylcyclopentanecarboxylates in good yields.In the copper-promoted reaction of1,3-diketones and2,3-allenoates, the unexpect4-carbonyl-3,5-dialkyl-3-(2-oxo-2-arylethyl)furan-2(3H)-ones product were obtained with the electron-deficient C=C bond beinig intramolecular attacked by the enolate nucleophiles. The allenoates served as a2C component to form the versatile five-membered rings.The rection of propiophenone and4-aryl-2,3-allenoates with Cu(OAc)2as the additive formed3-methyl-5-(1-oxo-1-phenylpropan-2-yl)-5-phenylfuran-2(5H)-one in moderate yield. We envisioned that the cross-dehydrogenative-coupling (CDC) reaction between propiophenone and3-methyl-5-phenylfuran-2(5H)-one derived from the cyclization of allenoate.Part â…¥:Some trials on addition of C=O bonds In the appendix, we showed our efforts on the addition reaction of arylpalladium species generated from oxidative addition of Pd(0) and arylhalide to C=O bond of aldehyde. Also, a base promoted reaction between aldehydes and2,3-allenoates was observed and further study are being carried out in our laboratory.