Acetophenone groups

Organon have developed Org 31710 and Org 33628 (Figure 7.2). Org 31710 has the same substituent at position 11 but differs at the 17-position, where it contains a spiro-ether group. In the B-ring, it has a 6P-methyl group. Org 33628 has a acetophenone group instead of a dimethylaminophenyl group and is combined with a methylene-furan substituent at position 17 [12]. 

It is generally accepted that acetophenone end-groups are formed during UV irradiation of polystyrene and it is most probable that they are responsible for the yellow coloration of a polymer. Molar absorptivity of acetophenone groups at 240nm is e= 1.4 x 10" lmol cm and the apparent quantum for their formation is = 9 x 10". They have an IR absorption band at 1685-1690cm- [745]. 

The acetophenone group gives phosphorescence [719, 725, 1211] and its spectrum is shown in Figure 3.55. 

Acetophenone groups absorb UV irradiation and may participate in a number of photochemical reactions ... 

Type I photoinitiators show considerable structural variety, one of the most common motives being the acetophenone group. The general structure of this kind of photoinitiators is shown in Scheme 1.5. 

TTie true ketones, in which the >CO group is in the side chain, the most common examples being acetophenone or methyl phenyl ketone, C HjCOCH, and benzophenone or diphenyl ketone, C HjCOC(Hj. These ketones are usually prepared by a modification of the Friedel-Crafts reaction, an aromatic hydrocarbon being treated with an acyl chloride (either aliphatic or aromatic) in the presence of aluminium chloride. Thus benzene reacts with acetyl chloride... 

The student should note that ketones in class (1), t.c., those having the >CO group in the side chain, will form additive compounds with sodium bisulphite only if this >CO group is not directly joined to the benzene ring acetophenone therefore will not form such compounds, whereas benzyl methyl ketone, CaHsCHjCOCH, will do so. Many quinones, particularly ortho quinones such as phenanthraquinone, form additive compounds with sodium bisulphite. 

The Mannich Reaction involves the condensation of formaldehyde with ammonia or a primary or secondary amine and with a third compound containing a reactive methylene group these compounds are most frequently those in which the methylene group is activated by a neighbouring keto group. Thus when acetophenone is boiled in ethanolic solution with paraformaldehyde and dimethylamine hydrochloride, condensation occurs readily with the formation of... 

Bisulphite addition compound. Shake 1 ml. of acetone with 0 5 ml. of a saturated solution of NaHS03. A white precipitate is formed, the mixture becoming warm and then, on cooling, almost solid. Acetophenone and benzophenone, having the >CO group directly joined to tlie benzene ring, do not respond to the test (p- 257). 

The type of synthesis in which the two-atom fragment supplies C-5 + C-6 is uncommon but useful in preparing pyrimidine- and 5,6,7,8-tetrahydroquinazoline-2,4-diamines. Thus, dicyandiamide (S78) with benzyl methyl ketone (S77) yields 6-methyl-5-phenylpyrimidine-2,4-diamine (S79), or with acetophenone it yields 6-phenylpyrimidine-2,4-diamine (62JOC2708). Likewise, with cyclohexanone it yields the tetrahydroquinazolinediamine (SSO) and by using N- substituted dicyandiamides, 2- and/or 4-alkylamino groups may be introduced (65JOC1837). 

The synthesis of pyrazolines and pyrazoles of the [CCNN + C] type with the creation of two bonds, N(2)-C(3) + C(3)-C(4) (or N(l)-C(5) + C(5)-C(4)), has been studied by several groups. Beam and coworkers have published a series of papers on the synthetic utility of lithiated hydrazones. Thus, the methylhydrazone of acetophenone (598) is converted by butyllithium into the dianion (599), which in turn reacts with methyl benzoate to afford the pyrazole (600) (76SC5). In earlier publications Beam et al. have used aldehydes and acyl chlorides to obtain pyrazolines and pyrazoles by the same method. 

Azirines react with enolate anions. Initial nucleophilic attack on phenyl 1-azirine by the enolate anion derived from acetophenone gives intermediate (223) which undergoes 1,2-bond cleavage, cyclization and hydroxyl group elimination to give pyrrole (226). 

Another example of enhanced sensitivity to substituent effects in the gas phase can be seen in a comparison of the gas-phase basicity for a series of substituted acetophenones and methyl benzoates. It was foimd that scnsitivtiy of the free energy to substituent changes was about four times that in solution, as measured by the comparison of A( for each substituent. The gas-phase data for both series were correlated by the Yukawa-Tsuno equation. For both series, the p value was about 12. However, the parameter r" ", which reflects the contribution of extra resonance effects, was greater in the acetophenone series than in the methyl benzoate series. This can be attributed to the substantial resonance stabilization provided by the methoxy group in the esters, which diminishes the extent of conjugation with the substituents. 

The leaving group in the alkylating reagent has a major effect on whether C- or O-alkylation occurs. In the case of the lithium enolate of acetophenone, for example, C-alkylation is predominant with methyl iodide, but C- and O-alkylation occur to approximately equal extents with dimethyl sulfate. The C- versus O-alkylation ratio has also been studied for the potassium salt of ethyl acetoacetate as a function of both solvent and leaving group. ... 

The rho values (2.78 overall, 3.78 for reduction to the cis product and 1.96 for reduction to the trans), determined from a study of the rates of reduction with NaBH4 of a series of 4-substituted cyclohexanones, have been interpreted as supporting a transition state late in the reaction.Other groups have observed positive rho values (2.5 to 3.1) for the reduction with NaBH4 of fluorenones and acetophenones. These results show clearly... 

Electrochemical reduction of carbon-fliionne bonds occurs at high pH when a carbonyl group is adjacent Polaiographic reduction of a a,a-tnfluoroacetophe-none without loss of fluonne predominates in acidic media to give the alcohol and the corresponding pinacol, whereas reduction of the unprotonated ketone results in hydrogenolysis of the tnfluoromethyl group to form acetophenone as product Il] (equation 8)... 

The acid-catalyzed reaction of acetophenone with acyclic secondary amines results in the formation of the expected enamine and a rearrangement product. The latter product arises from the transfer of one of the amino N-alkyl groups to the cnamine s carbon to produce a ketimine (53a). 

Spectroscopic investigation of enamines conjugated with ketone, ester and nitrile groups established the prevalence of enamine rather than imine-enol tautomers in examples of secondary amines (206-212). Similar studies have been made with enamines of acylpyridines and acetophenones (213,214). 

The tetrahydropyranyl ether, prepared from a phenol and dihydropyran (HCl/EtOAc, 25°, 24 h) is cleaved by aqueous oxalic acid (MeOH, 50-90°, 1-2 h). Tonsil, Mexican Bentonite earth, HSZ Zeolite, and H3[PW,204o] have also been used for the tetrahydropyranylation of phenols. The use of [Ru(ACN)3(triphos)](OTf)2 in acetone selectively removes the THP group from a phenol in the presence of an alkyl THP group. Ketals of acetophenones are also cleaved. ... 

The substitution of the lone proton on the benzhydryl carbon by a methyl group again affords compounds with antihistamine activity. Reaction of an appropriate acetophenone (21) with phenyl-magnesium bromide affords the desired tertiary alcohols (22). 

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