Zation

First the protected oligopeptide is coupled with polymer-bound nitrophenol by DCC. N"-Deblocking leads then to simultaneous cycliiation and detachment of the product from the polymer (M. Fridkin, 1965). Recent work indicates that high dilution in liquid-phase cycli-zation is only necessary, if the cyclization reaction is sterically hindered. Working at low temperatures and moderate dilution with moderately activated acid derivatives is the method of choice for the formation of macrocyclic lactams (R.F. Nutt, 1980). 

The benzene derivative 409 is synthesized by the Pd-catalyzed reaction of the haloenyne 407 with alkynes. The intramolecular insertion of the internal alkyne, followed by the intermolecular coupling of the terminal alkyne using Pd(OAc)2, Ph3P, and Cul, affords the dienyne system 408, which cyclizes to the aromatic ring 409[281]. A similar cyclization of 410 with the terminal alkyne 411 to form benzene derivatives 412 and 413 without using Cul is explained by the successive intermolecular and intramolecuar insertions of the two triple bonds and the double bond[282]. The angularly bisannulated benzene derivative 415 is formed in one step by a totally intramolecular version of polycycli-zation of bromoenediyne 414[283,284],... 

Sulfones and sulfoxides (145) are obtained usually from the corresponding sulfide by oxidation (Scheme 75) (341). though some of them were prepared from a halothiazole and metal sulfinate (342). 2-Amino-5-acetamidophenylsulfonylthiazole has been prepared by direct heterocycli-zation (343. 344). 

In all its reactions the lone pair of thiazole is less reactive than that of pyridine. Table 1-61 shows three sets of physicochemical data that illustrate this difference. These are (1) the thermodynamic basicity, which is three orders of magnitude lower for thiazole than for pyridine (2) the enthalpy of reaction with BF3 in nitrobenzene solution, which is 10% lower for thiazole than for pyridine and (3) the specific rate of quaterni-zation by methyl iodide in acetone at 40°C, which is about 50% lower for... 

TABLE in-52. KINETIC DATA FOR THE OUATERNI-ZATION OF 2- AND 4-ALKYLTHIAZOLES WITH METHYL IODIDE IN NITROBENZENE AT 25°C (256)... 

M. G. Reinecke, Tetrahedron 38, 427 (1982) R. Mumgan, Meta/Zation, Conformationa/Ana/ysis, Hydrogen Exchange and Rearrangement in Amides, Doctoral thesis. University of Plorida, Gainesville, 1987 A. Weissberger and E. C. Taylor, eds.. The Chemistry of Heteroyc/ic Compounds, in Ref. 11, pp. 448—449. 

CsH5)2Ti [1271-29-0] Ti(II) Cpj dark green 200 pyrophoric catalyst for polymeti-zation of olefins and acetylenes... 

Neutralization Acidic or basic wastewaters must be neutrahzed prior to discharge. If an industry produces both acidic and basic wastes, these wastes may be mixed together at the proper rates to obtain neutral pH levels. Equahzation basins can be used as neutralization basins. When separate chemical neutralization is required, sodium hydroxide is the easiest base material to handle in a hquid form and can be used at various concentrations for in-line neutralization with a minimum of equipment. Yet, lime remains the most widely used base for acid neutr zation. Limestone is used when reaction rates are slow and considerable time is available for reaction. Siilfuric acid is the primary acid used to neutralize high-pH wastewaters unless calcium smfate might be precipitated as a resmt of the neutralization reaction. Hydrochloric acid can be used for neutrahzation of basic wastes if sulfuric acid is not acceptable. For very weak basic waste-waters carbon dioxide can be adequate for neutralization. 

In order that the flowmeter may be used during an ozoni-zation when tube J is empty it is necessary to mark the heights of liquid on both tubes. The same liquid head (height X density) must be present in the absorption tubes during calibra-... 

Such a dipping apparatus can also be employed with advantage for applying substances to preserve or intensify fluorescence after chromatography or derivati-zation is complete (cf. Section 3.2.7.3). 

The Bergmann variation of the Balz Schiemann reaction is a two-step process featuring copper- or copper halide-catalyzed decomposition of aqueous or acetone solutions of arenediazonium fluoroborates containing alkyl or halogen substituents [30] A recent modification is a one-step technique featuring simultaneous diazoti-zation and decomposition by addition of aqueous sodium nitrite at 25 °C to a mixture of fluorobonc acid, copper powder, and 2 isopropyl 6 methylaniline to give 2-isopropyl-6 methylfluorobenzene in 73% yield [37]... 

CN/CC replacement has also been observed on treatment of pteridine with malonitrile or cyanoacetamide 6-amino-7-R-pyrido[2,3,-h]pyrazine (R = CN, CONH2) beingformed (73JCSP(1)1615) (Scheme 15). The reaction involves initial addition of the reagent to the N-3-C-4 bond, scission of the dihydro bond between N-3 and C-4 in the covalent adduct, and recycli-zation. This mechanism is fundamentally different from the mechanism mentioned in Scheme 14, where two molecules of the reagent were used for addition and where the bond breaking takes place between N-1 and C-2. 

The lack of structural specificity among sedative-hypnotic drugs has been alluded to before. It is perhaps not too surprising that quinazolones, too, show this activity. The prototype, methaqualone (149), is obtained in a single step from the condensation of the"anthranilamide, 148, with o-toluidine.(The reaction may well involve first formation of the bisamide cycli-zation will then give the quinazolone ring system.) Condensation... 

Catalytic processes frequently require more than a single chemical function, and these bifunctional or polyfunctional materials innst be prepared in away to assure effective communication among the various constitnents. For example, naphtha reforming requires both an acidic function for isomerization and alkylation and a hydrogenation function for aromati-zation and saturation. The acidic function is often a promoted porous metal oxide (e.g., alumina) with a noble metal (e.g., platinum) deposited on its surface to provide the hydrogenation sites. To avoid separation problems, it is not unusual to attach homogeneous catalysts and even enzymes to solid surfaces for use in flow reactors. Although this technique works well in some environmental catalytic systems, such attachment sometimes modifies the catalytic specifici-... 

---