Carbonylation direct

The efficiency of photon capture to form the l(nn ) state is very low since the excitation is electric dipole forbidden in the local C2V point group of the carbonyl. Direct... 

Alanine. Residues 4, 5, 56, 96, 102, and 109 CB clear in positive, but perhaps weak, electron density. Residues 6, 52, 64, 122 CB outside of lowest electron density contour or poorly defined. Residue 5 carbonyl direction apparently pointing somewhat away from helix axis with no obvious explanation. Residues 19 and 20 uncertain region of very poorly defined chain. 

Review H. M. Colquhoun, D. J. Thompson, M. V. Twigg, Carbonylation-Direct Synthesis of Carbonyl Compounds," Plenum, New York (1991)... 

Fluoro benzisothiazoles (6) were synthesized via carbonyl directed nucleophilic aromatic substitution. Displacement of the ortho fluoro substituent in 2,4-difluorobenzaldehyde, 2 4 -difluoroacetophenone and 2,4-difluorobenzophenone with benzyl mercaptan and potassium... 

Karabatsos, G. J. Asymmetric induction. A model for additions to carbonyls directly bonded to asymmetric carbons, J. Am. Chem. Soc. 1967, 89, 1367-1371. 

Vinyl sulfoxides mostly require a second electron-withdrawing groiq) to increase their dienophilic character. Thus vinyl sulfoxides bearing a carbonyl moiety at Cp undergo carbonyl-directed diene addition followed by a spontaneous elimination of sulfenic acid, as applied to a synthesis of disodium pre-phenate (74) (Scheme 21). ... 

Other proteases employ the same catalytic strategy. Some of these proteases, such as trypsin and elastase, are homologs of chymotrypsin. In other proteases, such as subtilisin, a very similar catalytic triad has arisen by convergent evolution. Active-site structures that differ from the catalytic triad are present in a number of other classes of proteases. These classes employ a range of catalytic strategies but, in each case, a nucleophile is generated that is sufficiently powerful to attack the peptide carbonyl group. In some enzymes, the nucleophile is derived from a side chain whereas, in others, an activated water molecule attacks the peptide carbonyl directly. 

Extraction of uranyl with all three amides was always much higher from the SCN solution than from the NOa" solution, possibly indicating a more stable U VSCN complex. IR spectra and H-NMR data confirm the bonding of the amide carbonyl directly to the metal ion in all three ligands. Lack of OH stretching modes in the IR spectra eliminates the presence of water in the extracted complexes. IR data also confirms direct bonding on NOs" and SCN to the metal. These analyses confirm the slope analysis observations." ... 

In the other sequence, EtMgBr is likely to add to the carbonyl direct and the further addition of HCI may either substitute on the allylic alcohol or add the wrong way round to the alkene. 

Colquhoun HM, Thompson DJ, Twigg MV (1991) Carbonylation. Direct synthesis of carbonyl compounds. Plenum Press, New York... 

Fig. 14.9. The principal axis system (PAS) orientation of the carbonyl carbon relative to the bonds of interest in PET. The crn axis corresponds to the normal of the carbonyl (O—C=0) plane. The 0-22 axis is set parallel to the carbonyl direction (C==0) in the carboxyl plane. The 0-33 axis is perpendicular to both crn and 0-33 directions. The angle 6 between the phenylene para-C—C and chain axes is also shown.

The following compounds are isomeric C-6 ketones. Complete identification should be possible by considering carbonyl-directed cleavages and the McLafferty rearrangement (or lack of it). Identify the compound using these processes. 

Olah et al. reported the triflic acid-catalyzed isobutene-iso-butylene alkylation, modified with trifluoroacetic acid (TFA) or water. They found that the best alkylation conditions were at an acid strength of about//q = —10.7, giving a calculated research octane number (RON) of 89.1 (TfOH/TFA) and91.3 (TfOH/HaO). Triflic acid-modified zeohtes can be used for the gas phase synthesis of methyl tert-butyl ether (MTBE), and the mechanism of activity enhancement by triflic acid modification appears to be related to the formation of extra-lattice Al rather than the direct presence of triflic acid. A thermally stable solid catalyst prepared from amorphous silica gel and triflic acid has also been reported. The obtained material was found to be an active catalyst in the alkylation of isobutylene with n-butenes to yield high-octane gasoline components. A similar study has been carried out with triflic acid-functionalized mesoporous Zr-TMS catalysts. Triflic acid-catalyzed carbonylation, direct coupling reactions, and formylation of toluene have also been reported. Tritlic acid also promotes transalkylation and adaman-tylation of arenes in ionic liquids. Triflic acid-mediated reactions of methylenecyclopropanes with nitriles have also been investigated to provide [3 + 2] cycloaddition products as well as Ritter products. Tritlic acid also catalyzes cyclization of unsaturated alcohols to cyclic ethers. ... 

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