Previously unknown presence

Discovery of previously unknown presence of a hazardous or toxic chemical in a product is reportable if widespread or significant exposure is substantially likely to occur and presents a substantial risk of injury to health... 

The NHCs have been used as ligands of different metal catalysts (i.e. copper, nickel, gold, cobalt, palladium, rhodium) in a wide range of cycloaddition reactions such as [4-1-2] (see Section 5.6), [3h-2], [2h-2h-2] and others. These NHC-metal catalysts have allowed reactions to occur at lower temperature and pressure. Furthermore, some NHC-TM catalysts even promote previously unknown reactions. One of the most popular reactions to generate 1,2,3-triazoles is the 1,3-dipolar Huisgen cycloaddition (reaction between azides and alkynes) [8]. Lately, this [3h-2] cycloaddition reaction has been aided by different [Cu(NHC)JX complexes [9]. The reactions between electron-rich, electron-poor and/or hindered alkynes 16 and azides 17 in the presence of low NHC-copper 18-20 loadings (in some cases even ppm amounts were used) afforded the 1,2,3-triazoles 21 regioselectively (Scheme 5.5 Table 5.2). 

The cycloaddition of nitrile oxides to nitriles in the presence of a Pd(ll) center allowed the isolation of the previously unknown l,2,4-oxadiazole-Pd(n) species 227 (Equation 44) <2005EJI845>. 

Rh s(CO)iis they revealed the presence of an unidentified complex which was suggested to be the previously unknown species Rh4(a-CO)i2-The BTEM protocol is an extremely powerful technique to recover pure component spectra of unknown species, even when present at very low concentrations. This was illustrated by a detailed mechanistic study of the promoting effect of HMn(CO)5 on the Rh4(CO)i2 catalyzed hydroformylation of 3,3-dimethylbut-l-ene [22], A dramatic increase in the hydroformylation rate was found when both metals were used simultaneously. Detailed in situ FTIR measurements using the BTEM protocol indicated the presence of homometallic complexes only during catalysis. The metal complexes that were identified under catalytic conditions were RC(0)Rh(C0)4, Rh4(CO)i2, Rh5(CO)i5, HMn(CO)s, and Mn2(CO)io (see Figure 6.6). The kinetics of product formation showed an overall product formation rate, Eq. (3) ... 

The first synthetic leather dyes were cationic. Mauveine, discovered by W. H. Perkin, marked the start of the synthetic dye industry. The cationic dyes were characterized by a previously unknown brightness. Nevertheless, the introduction of the new synthetic dyes was not a simple matter. The lightfastness properties were poor. However, the presence of Perkin at the first International Leather Congress in 1897 in London, undoubtedly ensured the breakthrough in the use of synthetic dyes for leather. 

The same paper describes the reaction of trialkyl phosphites with isatin arylazomethines in the presence of nickel or copper monohalides, leading to the previously unknown phosphorus-containing derivatives of 2-indolinone 68 ... 

The exceptionally facile epoxidation of allylic alcohols by tert-butyl hydroperoxide in the presence of vanadium catalysts, discussed earlier, has been used466,467 for the synthesis of complex molecules. Thus, geraniol (X) and linalool (XI) are selectively epoxidized to the previously unknown monoepoxides with f-Bu02 H-V 0(acac)2 466 ... 

It appears that use of the Wood formula for calculating Tg values combined with the use of literature data relating MFT and Tg was reliable for obtaining previously unknown MFT values despite the presence of small amounts of acid in the polymer and a likely difference in polymerization method. 

Our Interest In understanding the behavior of rhodium carbonyl clusters in systems which catalytlcally convert CO H2 Into alcohols 3. prompted us to test the potential presence of mononuclear and bI nuclear rhodium carbonyl complexes In these systems. A positive characterization of these species under these circumstances would show a previously unknown behavior of rhodium carbonyl clusters under high pressure of carbon monoxide. It could also show the existence of a parallel behavior between the chemistry of these species under ambient and high pressures of carbon monoxide, and it may shed some light on the catalytic reactions occurring in those systems. 3. ... 

We have synthesized previously unknown silocyne, silocane, and silatrane derivatives of acrylic acids according to Scheme la in the presence of polymerization inhibitors. Acrylates are also obtained by concurrent synthesis on the basis of previously described halomethylsilocanes via Scheme lb. 

In addition, it should be noted that results from these analyses of mushroom extracts indicated the presence of a previously unknown alkaloid, which I have named aeruginascin. The molecular stmcture of this substance must be similar to those of psilocybin and baeocystin. It is a compound that is soluble only in polar solvents, such as water, methanol and acetic acid. The levels of concentration of aemginascin found in the fmiting bodies is comparable to those of the other two alkaloids. The compound is characteristic of the Inocybe species, so that the analytical results of mushrooms extracts using thin-layer chromatography constitute a kind of fingerprint identification of Inocybe aeruginascem. 

Figure 4.35. Comparison of the spectrum of a previously unknown sialon phase with that of O-sialon. The diagnostic presence of oxynitride units in the new phase (- 61 ppm) has led to its identification as a low-temperature form of O-sialon. From Barris et al. (1997), by permission of...

Bicyclic Carotenoids. Re-investigation of the carotenoids of Anacystis nidulans has confirmed the presence of /3,)8-carotene-2,3,3 -triol (6), and the previously unknown )8,j8-carotene -2,3,2, 3 -tetrol (7) was also isolated. These compounds are considered to be identical with caloxanthin and nostoxanthin, for which allenic structures have previously been suggested. The main carotenoid of Coccolithus... 

Dibenzo[h./]oxepins and dibenzo[hJ]thiepins have important medicinal uses and can be prepared by irradiation of halogeno-substituted acetophones in liquid ammonia in the presence of bases (Nagaoka). A novel 1,9-hydrogen atom abstraction occurs on irradiation of 47 to give ultimately the keto ether 48 (Mizuno et al.) and previously unknown polycyclic ring systems such as 49,... 

---