Phenacyl 2,5 dimethyl

The reaction between dimethyl acetylenedicarboxylate and the zwitterion derived by the action of base on 1 -phenacyl-2,5-dimethyl-pyrazmium bromide gives mainly l,2-dimethoxycarbonyl-5,8-di-... 

Isotubaic acid — see Benzofuran-5-carboxylic acid, 4-hydroxy-2-isopropyl-Isouramil occurrence, 3, 144 5-Isoxalones potentiometry, 6, 11 Isoxanthopterin, 6-acetonyl-structure, 3, 276 Isoxanthopterin, 3,8-dimethyl-rearrangements, 3, 309 Isoxanthopterin, 6-methoxy-3,8-dimethyl-synthesis, 3, 297 Isoxanthopterin, 6-methyl-bromination, 3, 301 Isoxanthopterin, 8-methyl-synthesis, 3, 319 Isoxanthopterin, 6-phenacyl-structure, 3, 276... 

Xanthopterin, 7,7-dimethyl-7,8-dihydro-synthesis, 3, 315 Xanthopterin, 7-methyl-synthesis, 3, 303 Xanthopterin, 7-phenacyl-structure, 3, 276 Xanthopterin, 3,5,7-trimethyl-Claisen condensation, 3, 303 Xanthopterin-7-carboxylic acid reactions... 

Thiopyrones and selenopyrones can be alkylated more readily than pyrones. Thus 2,6-dimethyl-4/f-pyran-4-thionc (4,6-dimethyl-4-thiopyrone) (23, Y = S) reacts rapidly with methyl iodide yielding a 4-methylmercaptopyrylium iodide (24, Y = S, R = Me, X = I). Many alkylating agents were investigated by King et al. The kinetics of the reaction between 2,6-dimethyl-4-thiopyrone and substituted phenacyl bromides was found to be described by the Hammett... 

Ruveda, M.A. and deLicastro, S.A., Synthesis of dimethyl a-hydroxy phosphonates from dimethyl phosphite and phenacyl chloride and cyanide, Tetrahedron, 28, 6018, 1972. 

Quaternarization of 43 with phenacyl bromide produced the corresponding salt 51 that was reacted with several triple-bond-containing dipolarophiles (Scheme 4), such as dimethyl acetylenedicarboxylate (DMAD) or alkyl propiolates to give tricyclic compounds 52, 53 and 54, 55. Compound 51 reacted also with acrylonitrile as dipolaro-phile in MeCN/K2C03 to give the cycloadduct 56 as a mixture of diasteroisomers. 

Asymmetric induction using catalytic amounts of quininium or A-methyl-ephedrinium salts for the Darzen s reaction of aldehydes and ketones with phenacyl halides and chloromethylsulphones produces oxiranes of low optical purity [3, 24, 25]. The chiral catalyst appears to have little more effect than non-chiral catalysts (Section 12.1). Similarly, the catalysed reaction of sodium cyanide with a-bromo-ketones produces epoxynitriles of only low optical purity [3]. The claimed 67% ee for the phenyloxirane derived from the reaction of benzaldehyde with trimethylsul-phonium iodide under basic conditions [26] in the presence of A,A-dimethyle-phedrinium chloride was later retracted [27] the product was contaminated with the 2-methyl-3-phenyloxirane from the degradation of the catalyst. 

Treatment of the phenacyliminium salt 114, derived from 5,7-dimethyl[l,2,4]-triazolo[l,5-fl]pyrimidine 113 and phenacyl bromide, with 2 equiv of triethylamine gives rise to the 2-iminooxazoline 118 by way of the in situ generated intermediary A -ylides 115. Acidic hydrolysis affords the 3-(2-pyrimidinyl)-2(3//)-oxazolone... 

Reaction of 5,7-dimethyl-l,2,4-triazolo[l,5-a]pyrimidine (246) with phenacyl bromide gave the triazolopyrimidinium salt 247 (85JCS(P1)2333 85TL1321). Treating 247 with one equivalent of triethylamine gave the ylide 248, whose thermolysis in acetonitrile gave Af-cyano-lV-phenacylaminopy-rimidine (249), but when 247 was treated with two equivalents of triethylamine, the 2-iminooxazoline 250 was formed, which was also obtained from 249 by further treatment with another equivalent of triethylamine (Scheme 46). 

Hydrazino-l,3-dimethyluracil (185) reacts with phenacyl bromides in DMF to give the corresponding 3-aryl-6,8-dimethylpyrimido[4,5-c]pyridazine-5,7-diones (186). 6-Benzyl-idenehydrazino-l,3-dimethyluracils are also known to react with DMF dimethyl acetal to give pyrimido[4,5-c]pyridazines (78JHC781). 

N-Phenacyl-N -methylpiperazine Cyclohexyl bromide Magnesium Dimethyl sulfate... 

Zabadal, M., Pelliccioli, A.P., Klan, P. and Wirz, J. (2001) 2,5-Dimethyl-phenacyl esters A photoremovable protecting group for carboxylic acids. Journal of Physical Chemistry A, 105, 10329-10333. 

Dimethyl-l,8-naphthyridin-2(l//)-one with butyllithium followed by benzo-nitrile and then hydrochloric acid gave 5-methyl-7-phenacyl-l,8-naphthyr-idin-2(l//)-one (39) in contrast, the same substrate treated similarly, but with sodium amide/ammonia in place of butyllithium, gave the isomeric 7-methyl-5-phenacyl-l,8-naphthyridin-2(l//)-one (40) (49%).401... 

The same 6-amino-5-nitrosouracil is converted by phenacyl bromide-pyridine into a 6-hydroxy-7-phenyllumazines [77H(6)1907]. Condensation with phenacylidenetriphenylphosphoranes and dimethyl acetylenedicar-boxylate gives lumazine derivatives [76CC588 81 H( 15)757 82JHC949] (Scheme 67). 

There are numerous examples of quaternizing alkylations of imidazoles using such diverse reagents as alkyl, alkenyl or aralkyl halides, ethyl chloroacetate, phenacyl bromide or dimethyl sulfate. Since water is frequently held very tenaciously by imidazole quaternary salts the compounds are often best prepared in anhydrous conditions (e.g. dry benzene solvent in a dry nitrogen atmosphere) even though the reaction is commonly slower in non-polar solvents. 

Dimerization of ethyl 2-amino-2-cyanoacetate gives diethyl 5-aminoimidazole-2,4-dicar-boxylate (92) as in Scheme 53. At reflux temperatures in propanol, 1,1-dimethyl-1-phenacyl-hydrazinium bromide is converted into 2-benzyl-4-phenylimidazole (93). Again the cycliz-ation is a dimerization process (Scheme 53) (80AHC(27)24l). 

MeOOC COOMe PhCOCHjNHAr MeOH/CHCIj, 1/1 (b.p.) Dimethyl-l-(/7-bromophenyl)-4-phenyl-pyrrole-2,3-carboxylate (52), dimethyl phenacyl (p-bromoanilino) maleate (20) 487, 480, 462... 

Amino protecting groups fall into four broad categories nitrobenzyl (e.g., nitrobenzyloxy-carbonyl and 4,5-dimethoxy-2-nitrobenzyloxycarbonyl), phenacyl (e.g., 4-methoxyphen-acyloxycarbonyl), benzyloxycarbonyl (e.g., a,a-dimethyl-3,5-dimethoxybenzyloxycarbonyl), and arylsulfonamides (e.g., tosyl). All but the sulfonamides mask the amino group as a carbamate. Removal of the blocking moiety releases an unstable carbamic acid, which spontaneously decarboxylates to give the unprotected amine. 

A thiete intermediate (225a) was proposed in the photochemical reaction of dimethyl acetylenedicarboxylate with 225,and similar intermediates were proposed in the addition of thiones or dithioesters to heteroatom-substituted acetylenes. Thiete 227 was suggested as an intermediate in the reaction of 226 with carbon disulfide. Reactions of aryl vinyl sulfide derivatives (2,4,6-trinitrobenzenesulfonate of a phenylthiovinyl alcohol, a phenacyl derivative )... 

Dimethyi-l-phenacylpyrazinium bromide (from 2,5-dimethylpyrazine and phenacyl bromide) and dimethyl acetylenedicarboxylate has been shown to give 6-benzoyl-7,8-bis(methoxycarbonyl)-1,4-dimethylpyrroIo[ 1,2-a] pyrazine (25) and 7,8-bis(methoxycarbonyl)-l,4-dimethylpyrrolo[l,2-fl]pyrazine (26) (723), and 1,2,5-trimethylpyrazinium iodide and dimethyl acetylenedicarboxylate also gave a 1% yield of (26). Addition reactions of 2-methyl- (724), 2,6-dimethyl- (724), 2,5-dimethyl- (725), and 2,3,5,6-tetramethylpyrazine (725), with dimethyl acetylenedicarboxylate have also been investigated. 

The most versatile method for the preparation of this ring system is the condensation of an a-halocarbonyl compound with a 3-amino-l,2,4-triazine. For example, treatment of 3-amino-5,6-dimethyl-l,2,4-triazine (565) with phenacyl bromide (512) produced only (566) (65JHC287). In addition to a-haloketones, a-haloaldehydes (72JHCH57, 55MI41000), a-haloacetals (80Ml4iooo) and a-haloesters (79CHE1255) have been used. The direction of condensation is always as shown for the preparation of (566). 

The oxidants dimethyl sulfoxide and nitroso compounds react easily with oL-bromo ketones and convert them into a-dicarbonyl compounds. The reaction with nitroso compounds is usually carried out in the presence of pyridine and proceeds through a nitrone stage. Phenacyl bromide (a-bromoacetophenone) is thus transformed first into phenacylpyridinium bromide and further, with nitrosobenzene, into a-ketoaldonitrone, which is subsequently treated with hydroxylamine to give phenylglyoxal monoxime or with phenylhydrazine to give phenylglyoxal osazone [985] (equation 411). 

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