A new and efficient hypervalent iodine−benzyne precursor, (phenyl)[2-(trimethylsilyl)phenyl]iodonium triflate (10), is reported. The hypervalent iodine−benzyne precursor 10 is readily prepared by reaction of 1,2-bis(trimethylsilyl)benzene with a PhI(OAc)2/TfOH reagent system. Treatment of 10 with Bu4NF in CH2Cl2 at room temperature gives high yields of the benzyne adducts in the presence of a trapping agent such as furan, 2-methylfuran, anthracene, tetraphenylcyclopentadienone, or 1,3-diphenylisobenzofuran. Especially, the result of the reaction in the presence of furan indicates a quantitative generation of benzyne and its efficient capture by the furan. Similarly, methylbenzynes (22 and 27) are efficiently generated from the corresponding methyl-substituted (trimethylsilyl)phenyliodonium triflates (12 and 13). The preparation of the hypervalent iodine−benzyne precursors, the generation of benzynes, the trapping reactions, and the nature are described in detail together with the advantages of the present reagents over the previously reported benzyne precursors.

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The behavior and mechanism for erosion of glass-ionomer cements in organic-acid buffer solutions were studied as a function of time, pH, and citric-acid concentration. In acidic solutions, the dissolution of the cement was controlled by the diffusion of the eluted species in the cement matrix, which depended on H+ ion concentration. In citric-acid solutions, the dissolution of the cement was controlled by both the diffusion and the surface reaction between the acid anion and the eluted species. Contribution of the latter reaction was larger with the increase in the acid concentration.

Erosion of a glass ionomer cement in acetic (AA), lactic (LA), citric (CA) and hydrochloric acids (HA) was investigated by means of chemical analysis, SEM observation and infrared (IR) spectroscopy. The larger stability constants of the complex between the acid anions and Al or Ca, or the lower the pH of the acid solutions, the more Al, Ca, Na, Si and F were leached. SEM observation revealed that the cement matrix dissolved out in 0.01M CA and HA. White precipitates formed in 0.01M CA and HA after immersion of the cement. They were identified as hydrated silicious gels by IR spectroscopy