Ethers, carbonylation and

As the preceding examples indicate, the yields of these SOCI2 and PBr3 reactions are generally high, and other functional groups such as ethers, carbonyls, and aromatic tings don t usually interfere. We ll look at the mechanisms of these substitution reactions in the next chapter. 

Lignin contains interconnected aromatic and aliphatic rings [11] (see figure 5) and aliphatic chains containing about 30 percent oxygen by weight in the form of ether, carbonyl, and hydroxyl bonds. 

Higher aldehydes also react with natural rubber. The reaction works best with purified rubber. Additions take place without a catalyst at 180 °C or in the presence of AlCb-NaCl at 120 °C. These reactions can be carried out in the solid phase by milling the rubber with an aldehyde, like glyoxal. Heating in a pressure vessel above 175 C is required to complete the reaction. Infrared spectra of the products from reactions in solution show presence of ether, carbonyl, and hydroxyl groups. ... 

In medium and weak complexes, the visible band of the complex is overlapped by that of free diiodine. Methods have been developed [38, 39] for measuring accurately and easily the blue shift, hereafter called A v(7tg -> ct ). The results of these measurements [38,39,65] under standard conditions of solvent (heptane) and temperature (15 °C, in order to increase the intensity of the band of the complex) are presented in the last column of Table 5.26 for 7T bases, pyridines, nitriles, ethers, carbonyls and sulfur bases. 

Marko and co-workers reported the activity of monomeric, moisture and air-stable NHC-Pt such as 133 (Figure 13.15). When complex 133 was applied to the hydrosilylation of a variety of terminal alkenes, only the anti-Markovnikov adducts were obtained, with isomerization by-products representing less than 2% of the reaction products. This catalyst tolerated functional groups such as ethers, carbonyls and esters, but internal alkenes were inert under similar conditions. A related series of six- and seven-mem-bered ring-expanded NHC-Pt complexes 134 was tested in the hydrosilylation of 1-octene with bis(trimethylsiloxy)methylsilane excellent activity and regioselectivity were observed. ... 

Additional gas-phase reactivity data, such as gas-phase acidities of alcohols [41], proton affinities of alcohols and ethers [41], and proton affinities of carbonyl compounds [42] could equally well be described by similar equations. 

Numerous diamines and aromatic dianhydrides have been investigated. WhoUy aromatic Pis have been stmctiirally modified by incorporating various functional groups, such as ether, carbonyl, sulfide, sulfone, methylene, isopropjlidene, perfluoroisopropyUdene, bipyridyls, sdoxane, methyl phosphine oxide, or various combinations of these, into the polymer backbone to achieve improved properties. The chemistry and apphcations of Pis have been described in several review articles (4). 

The aromatic core or framework of many aromatic compounds is relatively resistant to alkylperoxy radicals and inert under the usual autoxidation conditions (2). Consequentiy, even somewhat exotic aromatic acids are resistant to further oxidation this makes it possible to consider alkylaromatic LPO as a selective means of producing fine chemicals (206). Such products may include multifimctional aromatic acids, acids with fused rings, acids with rings linked by carbon—carbon bonds, or through ether, carbonyl, or other linkages (279—287). The products may even be phenoUc if the phenoUc hydroxyl is first esterified (288,289). 

Most metal carbonyls are synthesized in nonaqueous media. Reactive metals, such as sodium (85), magnesium (105), zinc (106), and aluminum (107,108), are usually used as reducing agents. Solvents that stabilize low oxidation states of metals and act as electron-transfer agents are commonly employed. These include diethyl ether, tetrahydrofiiran, and 2-methoxyethyl ether (diglyme). 

Semicrystalline Polyimides. Semicrystalline polyimides containing carbonyl and ether groups have been synthesized by the group at the NASA Langley Research Center (37). One such material, designated LARC-CPI, which is an acronym for Langley Research Center—Crystalline Polyimide,... 

For non-hydrogen-bonding polar compounds such as carbonyls and ethers, Tsonopoulos recommends that Eq. (2-68) be expanded to a third term that is a function of the reduced dipole moment ( I ) as described by Eqs. (2-71) through (2-73) ... 

Some of the original work in the carbohydrate area in particular reveals extensive protection of carbonyl and hydroxyl groups. For example, a cyclic diacetonide of glucose was selectively cleaved to the monoacetonide. A summary describes the selective protection of primary and secondary hydroxyl groups in a synthesis of gentiobiose, carried out in the 1870s, as triphenylmethyl ethers. 

The interposition of a syn-oximino ether moiety between the amide carbonyl and the aromatic ring has proved richly... 

If the carbonyl and the hydroxyl group are in the same molecule, an intramolecular nucleophilic addition can take place, leading to the formation of a cyclic hemiacetal. Five- and six-membered cyclic hemiacetals are relatively strain-free and particularly stable, and many carbohydrates therefore exist in an equilibrium between open-chain and cyclic forms. Glucose, for instance, exists in aqueous solution primarily in the six-membered, pyranose form resulting from intramolecular nucleophilic addition of the -OH group at C5 to the Cl carbonyl group (Figure 25.4). The name pyranose is derived from pyran, the name of the unsaturated six-membered cyclic ether. 

Dichloromethyl methyl ether may be employed preparatively in various ways. Thus it effects the replacement of carbonyl and hydroxyl oxygens by chlorine,11 and may be used in the preparation of a-acetochlorosugars 12 and acid chlorides, particularly those derived from acetylated monocarboxylic acid sugars 12 13... 

With the co side chain at C-12 in place, we are now in a position to address the elaboration of the side chain appended to C-8 and the completion of the syntheses. Treatment of lactone 19 with di-isobutylaluminum hydride (Dibal-H) accomplishes partial reduction of the C-6 lactone carbonyl and provides lactol 4. Wittig condensation8 of 4 with nonstabilized phosphorous ylide 5 proceeds smoothly and stereoselectively to give intermediate 20, the bistetra-hydropyranyl ether of ( )-1, in a yield of -80% from 18. The convergent coupling of compounds 4 and 5 is attended by the completely selective formation of the desired cis C5-C6 olefin. 

The pharmaceutical interest in the tricyclic structure of dibenz[6,/]oxepins with various side chains in position 10(11) stimulated a search for a convenient method for the introduction of functional groups into this position. It has been shown that nucleophilic attack at the carbonyl group in the 10-position of the dibenzoxepin structure renders the system susceptible to water elimination. Formally, the hydroxy group in the enol form is replaced by nucleophiles such as amines or thiols. The Lewis acids boron trifluoride-diethyl ether complex and titanium(IV) chloride have been used as catalysts. 

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