Aryl carbonylation

Polarization and dipole moment studies for alkyl-, aryl-, carbonyl- hydroxy- (keto-) and amino-isoxazoles have been compiled and likewise support the low electron nature of the ring 63AHC(2)365, 62HC(l7)l,p. 177). More recent studies predict the order of electrophilic substitution to be 5>4> 3 on frontier electron density values of 0.7831, 0.3721 and 0.0659, respectively 7lPMH(4)237,pp.245,247). This contrasts with earlier reports of 4>5>3 on density values of —0.09, -t-0.14 and -t-0.18 in that order 63AHC(2 365). 

A multitude of 1,4-dicarbonyls (1) undergo the Paal-Knorr reaction with and ranging from H to alkyl, aryl, carbonyl, nitrile, and phosphonate, while R and R vary between H, alkyl, aryl, trialkylsilyl, and O-alkyl. Protic acid catalysts are typically used with sulfuric, hydrochloric, and p-toluenesulfonic acids the most popular. Conversion to the furan takes place either at room temperature or upon heating with reaction times varying from five minutes to 24 hours and yields ranging from 17-100%. 

Reduction of unsaturated carbonyl compounds to the saturated carbonyl is achieved readily and in high yield. Over palladium the reduction will come to a near halt except under vigorous conditions (73). If an aryl carbonyl compound, or a vinylogous aryl carbonyl, such as in cinnamaldehyde is employed, some reduction of the carbonyl may occur as well. Carbonyl reduction can be diminished or stopped completely by addition of small amounts of potassium acetate (i5) to palladium catalysts. Other effective inhibitors are ferrous salts, such asferroussulfate, at a level of about one atom of iron per atom of palladium. The ferrous salt can be simply added to the hydrogenation solution (94). Homogeneous catalysts are not very effective in hydrogenation of unsaturated aldehydes because of the tendencies of these catalysts to promote decarbonylation. 

Aldehydes and ketones are similar in their response to hydrogenation catalysis, and an ordering of catalyst activities usually applies to both functions. But the difference between aliphatic and aromatic carbonyls is marked, and preferred catalysts differ. In hydrogenation of aliphatic carbonyls, hydrogenolysis seldom occurs, unless special structural features are present, but with aryl carbonyls either reduction to the alcohol or loss of the hydroxy group can be achieved at will. 

Muzart et al. described the coupling of aryl iodides and bromides with allylic alcohols to give the corresponding (3-arylated carbonyl compounds [87]. Calo et al... 

S. J. W. Price Decomposition of metal alkyls, aryls, carbonyls and nitrosyls, pp. 197-257 (156) see especially section 2, homogeneous decomposition of metal carbonyls, and section 3.1, homogeneous decomposition of metal alkyls and aryls (of Cu, Ag, Au). 

As is the case with aryl carbonyls previously studied, aliphatic carbonyls add to olefins to form oxetanes. The picture in this case is far more complicated, however, primarily due to the increased importance of singlet state carbonyl addition to the olefin. In Chapter 1 we saw that in an n->v ... 

All of the elements of stereo- and regioselectivity and reactivity that theory must explain are found in the above reactions. The triplet excited states of the aryl carbonyl compounds demonstrate regioselectivity that has been previously explained on the basis of the relative stabilities of the two possible biradical intermediates, 1 and 2. 65>66> The selectivity... 

Quinazolines undergo many of the same reactions as pyrimidines, such as the modification of an amino group. Gangjee and co-workers reported the reductive alkylation of diaminoquinazolinones 141 with various aryl carbonyl compounds 142, which regioselectively produced quinazolinones 143 <00JHC1097>. 

Aryl(carbonyl)carbenes. The mechanism of proton transfer to the carbenes 168 was found to respond sensibly to the ApA"a of the reactants. LFP of 167a generated 168a (A. = 355 nm) whose absorption was quenched rapidly by... 

The Decomposition of Metal Alkyls, Aryls, Carbonyls and Nitrosyls... 

DECOMPOSITION OF INORGANIC OXIDES AND SULPHIDES HALIDES AND DERIVATIVES METAL ALKYLS, ARYLS, CARBONYLS AND NITROSYLS... 

Carbonyl Complexes.—n-Aryl carbonyl complexes are included in this section. 

Redaction of aryl carbonyl compounds.2 This reduction has been conducted traditionally by the Clemmenson or Wolff-Kishner method or by reduction of dithioketals. Actually it can be conducted in high yield with W-7 Raney nickel in 50% aqueous ethanol (2-5 hours). Nitro, halo, and cyano groups are also reduced. Examples ... 

Janssen, P. (Janssen) 1-Arylalkyl-4-(N-aryl-carbonyl amino)-piperidiens and related compounds, US 3 164 600, 1965 ... 

The catalytic 1,6-addition of arylboronic acids to electron-deficient dienes, such as ( )-MeCH=CHCH=CHCOMe, was realized by use of an iridium catalyst. High yields of the corresponding 5-arylated carbonyl compounds were obtained with perfect 1,6-selectivity.249... 

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