Studies On Propargyl Alcohols (Esters) In Tandem Reaction

This thesis mainly aims at the studies on the propargyl alcohol and propargyl alcohol acetate derivatives in the tandem reaction, which includes two main parts.PartⅠ:Investigation on propargyl alcohol derivatives in the tandem cyclization reaction.Meyer-Schuster rearrangement, one of the well-known rearrangements, leads to tremendous change in molecular structures. The starting compound containing the hydroxyl and alkynyl functional groups can be removed the hydroxyl group to afford propargylic carbocation in the presence of proton acid, Lewis acid and transition metal. The propargyl carbocation keeps balance with allene cation, which is attacked by hydroxyl group and then tautomerization intoα,β-unsaturated carbonyl compoundsBased on this point (the propargyl carbocation keeps balance with allene cation), we have totally studied on a series of propargyl alcohol derivatives, including 1,4-butyne-diol, pent-2-yne-1,5-diol,4-aminobut-2-yn-l-ol,5-en-2-yn-l-ol,1,6-enyne-ol derivatives.1. Highly substituted dihalogenated dihydrofurans, dihydropyrroles, and dihydro-2H-pyrans have been obtained in good to excellent yields from simple starting materials by the electrophilic cyclization of 1,4-butyne-diols,4-aminobut-2-yn-l-ols and pent-2-yne-1,5-diols by electrophiles (I2, EBr and IC1) at room temperature. Additionally, six-membered cyclic products of high value including 2,3-diiodobenzenes were formed through iodonium-induced carbocyclizations of 5-en-2-yn-l-ols. The key step of these reactions is that the electrophile with water produces the proton to remove the hydroxyl group of propargyl alcohol derivatives and afford the propargyl cation. Next, these reactions are generally believed to proceed by a stepwise process involving the allene cation intermediate formation, which can be readily trapped by nucleophiles instead of water(e.g., C1, Br, I), electrophilies activation of the halogenated allene intermediate carbon-carbon double bond, intramolecular nucleophilies (C, N and O) attack on the cationic intermediate to give a series of substituted dihalogenated compound.2. We found a mild and direct process for C-C bond formation from 1,5-enyne-ol derivatives toward five-memeberd heterocyclic allene alcohols and 1,3-dienes compounds selectively in the presence of AgSbF6 catalyst. Further more, when 1 mol% TfOH was used as catalyst, one different type of five-memeberd heterocyclic allenes was synthesis selectively. To our surprised, when (E)-2-ethylidene-l-(6-en-1-yn-1-yl)cyclohexanol derivatives were carried out in the presence of HSbF6, several five-membered polycyclic skeletons were obtained in good to excellent. The key step of these reactions is that unactivated olefins attack on allene carbocation to form C-C bonds.In summary, we have developed several novel methods to construct benzene rings, heteroatom rings and sprio and polycyclic skeletons, which is useful in synthesis natural and artificial products.PartⅡ:Investigation on propargyl alcohol acetate derivatives in the tandem reaction.As the 6th period later transition elements, gold and platinum, in its high state, the central metal ion has an empty d-orbital can coordinate with rich electron donor and act as transition metals. Also, they are Lewis acids. They show high affinity for polarizingπ-bonds of the alkyne group, even in the presence of many other rich electron donors. After coordinating to gold and platinum, alkyne is polarized to active intermediates with dual cationic-carbenoid character, which react with nucleophiles or undergo the skeletal rearrangement to achieve the depolarization.Based on this point, we have totally studied on a series of propargyl alcohol acetate derivatives, including epoxy alkynes acetate,1,6-enyne-ol acetate derivatives.1. We have achieved the activation of alkynes by simple gold catalyst, which induced an intramolecular nucleophilic attack of an epoxide group to afford the oxonium ion intermediate. After capturing an intermolecular nucleophile-H2O, the depolarization of oxonium ion was achieved. The observation shows the property of the transition metal of gold. The intermediate furan alcohols can leave the hydroxyl group to afford carbocation in the presence of gold catalyst, which shows the property of Lewis acids.Various substituted furan compounds were synthesis through an intramolecular Friedel-type reaction. Based on this point, we added furan, methyl furan, indole, pyrrole and so on to capture the carbocation intermediate. Thus various substituted furan derivatives were obtained through an intermolecular Friedel-type reaction.2. A novel method for the selective synthesis of (Z)-1,5-dien-2-yl esters has been developed though Pt(II)-catalyzed tandem 1,2-acyl and 1,2-hydride migration, along with an ally] migration reaction of 1,6-enyne-ol carboxylates with electronically unbiased internal alkynes. We studied the scope of this reaction and the effect of different protective groups. We first reported the Pt(II)-catalyzed tandem triple migration reaction.