3/3-benzyloxy

To a stirred, ice-cold solution of 33.6 g of the above impure 2-benzyloxy-1,3-dimethoxy-5-propenylbenzene and 13.6 g pyridine in 142 ml acetone, there was added 24.6 g tetranitromethane. After stirring for 3 min, there was added a solution of 7.9 g KOH in 132 ml H20, followed by additional H20. The oily phase that remained was H20 washed, and then diluted with an equal volume of MeOH. This slowly set up to yellow crystals, which were removed by filtration and washed sparingly with MeOH. There was obtained 9.2 g 1-(4-benzyloxy-3,5-dimethoxyphenyl)-2-nitropropene with a mp of 84-85 deg C. An analytical sample, from EtOH, had a mp of 86-87 deg C. 

Also obtained by cleavage of 1 -(4-benzyloxy-3-methoxy-phenyl)-2-phenylethanone with 30% HBr in acetic acid/ methylene chloride (91%) [6231]. 

The protecting group Y of the amine is generally an alkoxycarbonyl derivative since their nucleophilicity is low. Benzyloxy- or tert-butoxycarbonyl derivatives usually do not undergo azlactone formation. 

J.M.J. Frechet (C. J. Hawker, 1990) replaced the divergent synthesis by a convergent growth of a dendritic polymer. The repeatedly employed monomer, 5-hydroxymethyl-l, 3-benzenediol, was 1,3-O-dibenzylatcd with 3,5-bis(benzyloxy)benzyl bromide. The resulting benzyl alcohol containing 7 benzene rings was converted to the benzyl bromide which was... 

The wM-diacetate 363 can be transformed into either enantiomer of the 4-substituted 2-cyclohexen-l-ol 364 via the enzymatic hydrolysis. By changing the relative reactivity of the allylic leaving groups (acetate and the more reactive carbonate), either enantiomer of 4-substituted cyclohexenyl acetate is accessible by choice. Then the enantioselective synthesis of (7 )- and (S)-5-substituted 1,3-cyclohexadienes 365 and 367 can be achieved. The Pd(II)-cat-alyzed acetoxylactonization of the diene acids affords the lactones 366 and 368 of different stereochemistry[310]. The tropane alkaloid skeletons 370 and 371 have been constructed based on this chemoselective Pd-catalyzed reactions of 6-benzyloxy-l,3-cycloheptadiene (369)[311]. 

An important reaction parameter is the choice of the base and NajCO or NaOAc have been shown to be preferable to EtjN in some systems[2]. The inclusion of NH4CI has also been found to speed reaction[2]. An optimization of the cyclization of A -allyl-2-benzyloxy-6-bromo-4-nitroaniline which achieved a 96% yield found EtjN to be the preferred base[3]. The use of acetyl or inethanesulfonyl as N-protecting groups is sometimes advantageous (see Entries 4 and 5, Table 4.1). 

Benzyloxy-6-bromo-4-nitro-JV-(2-propeny])aniline (5.82 g, 16 mmol), tetra-ii-butylammonium bromide (5.16 g, 16 mmol) and titjN (4.05 g, 40 mmol) were dissolved in DMF (15 ml). Palladium acetate (72 mg, 2 mol%) was added and the reaction mixture was stirred for 24 h. The reaction mixture was diluted with EtOAc, filtered through Cclite, washed with water, 5"/o HCl and brine, dried and evaporated in vacuo. The residue was dissolved in CHjClj and filtered through silica to remove colloidal palladium. Evaporation of the eluate gave the product (4.32 g) in 96% yield. 

Benzyloxy-5-methoxy-6-methyl Methyl Xylene/reflux 80,96 [10]... 

To a stirred ice-cooled solution of 2-(dimethylamino)-l-nitroethene (1.67 g, 14.4mmol) in TFA (7.2ml) was added 6-benzyloxy-l-methylindole (3.42g, 14.4 mmol). The solution was allowed to warm to room temperature and poured into ice water. The product was extracted using EtOAc to give 6-benzyloxy-l-methyl-3-(2-nitroethenyl)indoIe (4.2 g, 95%). 

Oxidative dimerization of various 2-benzyloxy-2-thiazoline-5-ones (222) catalyzed by iodine and triethylamine is another example of the nucleophilic reactivity of the C-4 atom (469) (Scheme 112). Treatment of 212 with pyrrolidinocyclohexene yields the amide (223) (Scheme 113). The mechanism given for the formation of 223 is proposed by analogy with the reactivitx of oxazolones with enamines (4701. 4-Substituted 2-phenylthiazol-5(4Hi-ones react with A -morphoiino-l-cyclohexene in a similar manner (562j. Recently. Barret and Walker have studied the Michael addition products... 

Benzylthio or 2-benzyloxy derivatives of A-2-thiazoline-5-one (224) are readily opened by amines to give the amide derivatives (225) (Scheme 115) (459. 471). Compound 225 can be cyclized thermally to the corresponding thiohydantoins (459). Similarly, treatment of 4-substituted-2-phenylthiazol-5(4H)-ones (226) with amino acids, peptides, or hydrazine affords the corresponding Nfcti-thiobenzamidoacetylated derivatives (227) (Scheme 116) (455). 

The reaction of the 2-benzyloxy thiazolinone (232) with (COCOo gives... 

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