Synthesis of γ,δ-Unsaturated Esters and Amides via Au(I)-Catalyzed Reactions of Aryl Ynol Ethers or Ynamides with Allylic Alcohols

Polarized alkynes such as ynol ethers and ynamides have attracted much attention due to their inherent unique reactivity. Herein, we report Au(I)-catalyzed hydroalkoxylation/Claisen rearrangement cascade reactions of aryl ynol ethers and ynamides with allylic alcohols. At the first stage (hydroalkoxylation) of this cascade reaction, attack of allylic alcohols to aryl ynol ethers or ynamides occurs at the α-position of the polarized alkynes in an entirely regioselective manner. Claisen rearrangement of the resulting adducts subsequentially takes place to give γ,δ-unsaturated esters or amides, respectively. The [Au(IPr)NTf2] catalyst is most effective for this reaction, and the reaction proceeds under mild conditions (in the case of aryl ynol ether: in THF, 60 °C; in the case of ynamides: in toluene, 80 °C) in an atom-economical way.

Diagnosis of concrete structures distress due to alkali-aggregate reaction

Damage and defects observed in concrete elements, such as a network of microcracks, popouts and eflorrescence can be caused by a variety of deleterious processes. The causes can include mechanical (overloading), physical (freeze-thaw cycle) or chemical exposure (sulphate corrosion, alkali-aggregate reaction). This paper analyses distress due to alkali-silica reaction, detected in selected concrete structures. The analysed concrete elements exhibited cracking, exudations and surface popouts. Identification of the presence of hydrated sodium-potassiumcalcium silicate gel can be considered the primary symptom suggestive of an alkali-silica reaction attack. Other damage-causing mechanisms can occur simultaneously.

Idealism and realism: beyond the great debate

The tendency of all debates is to exaggerate and to overkill, to claim and condemn too much. Then when the smoke has lifted and guns have been silenced, those who remain discover that the world is more complex and answers less certain than the debaters had led them to believe. It is as though worthy causes could not advance unless carried on the backs of overstatements. Think back in your lifetime to the progress which has been made toward desired ends: minority rights, women's liberation, the rights of the working man. Whenever movement has occurred, it has come in response to politics, propaganda and pressures. It has come because someone with a credible, sometimes noble cause planned and organized, but in their action almost always overdid at the price of generating reaction and counterattack. It may be stretching a point to compare thinking and political movements with wars and yet there is action and reaction, attack and counterattack in all three areas reminding us of Sir Herbert Butterfield's words: