Bromoacetaldehyde acetal

Alkylation of 395 with a-bromoacetaldehyde acetal (80MI1) or 2-bromoethanol (79KFZ61) gave alkylated derivatives 400 and 402, re-... 

Construction of the imidazole ring onto a triazine has been also used for the synthesis of this group of compounds. The reaction of 3-aminobenzofl, 2,4]triazine with a-bromoacetaldehyde acetal gave the [1,2-b] linear isomer. On the other hand, the similar reaction on 1-oxide 461... 

Bromoacetaldehyde acetals cannot be applied directly under the reaction conditions. However, when anhydrous Lil was used as an additive the cyclizations proceeded smoothly, probably by an initial Finkelstein reaction [107]. 

Salicylamide undergoes 0-alkylation on heating with bromoacetaldehyde acetal the product is then cyclized by heating. 

Both benzo[fc]furans and benzo[fc]thiophenes can be obtained from the phenol or thiophenol respectively, by O-Zi -alkylation with a bromoacetaldehyde acetal and then acid-catalysed ring closure involving intramolecular electrophilic attack on the ring. 

In order to produce hetero-ring unsubstituted benzothiophenes an arylthioacetaldehyde acetal is generally employed, prepared in turn, from bromoacetaldehyde acetal and the thiophenol. An exactly parallel sequence produces 2,3-unsubstitutedbenzofurans. 2-Aryloxy-acetates (or 1-aryloxy-acetones) heated with DMFDMA, produce enamines which cycUse on treatment with zinc chloride, giving 3-unsubstituted benzofuran-2-carboxylates (3-unsubstituted 2-acetyl-benzofurans). ... 

In order to produce hetero-ring unsubstituted benzothiophenes an arylthioace-taldehyde acetal is generally employed prepared, in turn, from bromoacetaldehyde acetal and the thiophenol. An exactly parallel sequence produces 2,3-unsubstituted... 

Laurino examined a similar method in which methanesulfonanilides were alkylated with bromoacetaldehyde diethyl acetal and then cyclized with TiCU[4J. 1 hese methods presumably involve generation of an electrophilic intermediate from the acetal functionality, followed by an intramolecular Friedel-Crafts reaction. As a consequence, the cyclization is favoured by ER substituents and retarded by EW groups on the benzene ring. 

Disubstituted furans are available from the combination of P-dicarbonyl compounds with bromoacetaldehyde diethyl acetal (44). For example, dibenzoylmethane (45) reacts with acetal 44 to furnish 2,3-disubstituted furan 46 in 77% yield. This two-... 

The benzazepines, veri 1 opam (79) and anilopam (81), for example, represent significant departures from the above generalization. Construction of the former starts with the alkylation of veratrylamine (74) with the dimethyl acetal of bromoacetaldehyde to give the secondary amine 7, Cyclization under acidic conditions leads to the benzazepine... 

Treatment of 2- 5//-dibenz[i>,/]azepin-5-yl acetaldehyde (16), prepared in 68% yield by /V-alkylation of 5/7-dibenz[A,/]azepine with bromoacetaldehyde diethyl acetal followed by acid hydrolysis, with methyl hydroxylamine yields the isolable nitrone 17, which in refluxing toluene undergoes intramolecular 1,3-dipolar cycloaddition at the CIO —Cl 1 alkene bond to give 2,3,3a, 12b-tetrahydro-2-methyl-3,8-methano-8//-dibenz[i>,/]isoxazolo[4,5-r/]azepine (18).235... 

The acetal 1, obtained from salicylamide and bromoacetaldehyde diethyl acetal, cyclizes on heating to provide l,4-benzoxazepin-5(4//)-one (2).32... 

Similarly, the monothione 24 reacts with acetylhydrazine to give the [l,2,4]triazolo[4,3-a][l,5]benzodiazepinone 25 with prop-2-ynamine the imidazo[1,2- ][1,5]benzodiazepinone 26 is produced and bromoacetaldehyde diethyl acetal provides the thiazolo[3,2-a][l, 5]ben-zodiazepinonc 27.282... 

Similarly, bromoacetaldehyde ethylene acetal with 3-aminobenzo [l,2,4]triazines 403 gave (82JHC61) linear tricyclic imidazobenzo[l,2,4] triazines 404 (Scheme 88). 

Benzothiophenes have always been of interest for medicinal chemistry and can be found in a number of marketed drugs such as Sertaconazole (Gineder-mofix), Zileuton (Leutrol) and Raloxifene (Evista). The classical synthesis of benzo thiophenes starts from thiophenols, reacting with bromoacetaldehyde dimethyl acetal, followed by cycUzation using strong acid. An alternative and more convenient route was also described starting from benzaldehydes which... 

BrN3 13973-87-0) see Cefoxitin bromoacetaldehyde diethyl acetal (C6H 3Bt02 2032-35-1) see Domiodol bromoacetaldehyde ethylene acetal (C4H7Br02 4360-63-8) see Carbimazole IV-bromoacetamide... 

Radical cyclization reactions have been extensively applied in synthesis. Among the first systems to be studied were unsaturated mixed acetals of bromoacetaldehyde.323... 

Two sequential lithiations and treatments with different bifunctional electrophiles make possible one-pot syntheses of relatively complex molecules. Thus, in the [1+2+2] annulation depicted in Scheme 69, alkylation of 1-benzylbenzotriazole 399 with 2-bromoacetaldehyde diethyl acetal to give intermediate 426 is followed by alkylation with W-benzylideneaniline to produce derivative 427. Following treatment with formic acid causes cyclization to ethoxypyrrolidine 428 that subsequently eliminates ethanol and benzotriazole to give pyrrole 429 <1997JHC1379>. 

Bromoacetaldehyde diethyl acetal, b317 Bromoanisoles, b357, b358, b359... 

The literature is replete with synthetic methods to prepare 5-bromofurans. One of the more practical syntheses [10, 11] commenced with etherification of 4-bromophenol with bromoacetaldehyde diethyl acetal using either NaH in DMF or KOH in DMSO. Treatment of the resulting aryloxyacetaldehyde acetal with polyphosphoric acid (PPA) afforded 5-bromofuran in good yield via intramolecular cyclocondensation. However, cyclization of m-aryloxyacetaldehyde acetal 1 resulted in a mixture of two regioisomers, 6-bromofuran (2) and 4-bromofiiran (3). Finally, 7-bromofuran 5 can be prepared similarly using the intramolecular cyclocondensation of aryloxyacetaldehyde acetal 4 generated from etherification of 2-bromophenol with bromoacetaldehyde diethyl acetal. 

Fuostifoline (47), a furo[3,2-a]carbazole, was isolated from Murraya euchrestifolia. Timdri s total synthesis of 47 commenced with alkylation of bromocresol 43 with bromoacetaldehyde diethyl acetal and P4Oio-promoted cyclization to furnish 5-bromo-7-methylbenzofuran (44) [47]. The Suzuki coupling of boronic acid 45, derived from 44, with o-bromonitrobenzene yielded biaryl 46. Nitrene generation, achieved via deoxygenation of nitro compound 46 using triethyl phosphite, was followed by cyclization to fuostifoline (47). 

A reported procedure based on lithium diisopropylamide induced double elimination of ethanol from bromoacetaldehyde diethyl acetal also was not very effective for the large scale preparation of phenylthioacetylene.8 Another more recent synthesis of the title compound relies on the reaction of dimethyl(chloroethynyl)carbinol with an alkali metal phenylthiolate, followed by... 

Bromination of o-cresol (1133) led to 5-bromocresol (1134), which, on alkylation with bromoacetaldehyde diethyl acetal, followed by P20s-promoted cyclization in... 

Dann and Dimmling showed that (2,5-dimethyl-3-thienylthio)acetic acid (86) may by cyclized to 4,6-dimethyl-2,3-dihydrothieno[3,4-6]-thiophen-3-one (87) by anhydrous hydrogen fluoride, and then reduced to 4,6-dimethylthieno[3,4-b]thiophene (88). The latter was obtained by cyclization of acetal (89) synthesized from 3-mercapto-2,S-c ethylthiophene (90) and bromoacetaldehyde dimethylacetd using hydrogen fluoride at 70°-80°. The synthetic route is illustrated by Scheme 6. 

The ozonolysis reaction, followed by reductive workup with sulfur dioxide, as described in Part A of the present procedure, illustrates a general method which has been developed for the preparation of acetals.3 Application of the procedure is illustrated by conversion of the following olefins in alcoholic solution to the corresponding acetals 3 (1) l-chloro-4-(o-nitrophenyl)-2-butene to o-nitrophenylacetaldehyde dimethyl acetal in 84% yield (2) l,4-dibromo-2-butene to bromoacetaldehyde dimethyl acetal in 67% yield (3) 3-butenoic acid to malonaldehydie acid diethyl acetal ethyl ester in 61% yield (4) cyclopentadiene to malonaldehyde bis(diethyl acetal) in 48% yield and (5)... 

A. Diethyl 2,2-Diethoxyethylphosphonate (Note 1). Into a 2-1., three-necked round-bottomed flask fitted with a magnetic stirrer, dropping funnel, and nitrogen inlet is placed 410 g. (2.08 moles) of bromoacetaldehyde diethyl acetal (Note 2), and a gentle stream of nitrogen is then passed continuously through the system. To the stirred solution is added dropwise 316 g. (1.90 moles) of triethyl phosphite (Note 3) over a period of 30 minutes, at 110-120°. The mixture is then stirred for 3 hours at 160°. The ethyl bromide evolved is trapped by a condenser and a receiver cooled in an ice bath. The low-boiling... 

Hydroxybenzyl alcohols have been converted to dioxepins, as the major product, by forming methoxyethoxy-methyl (MEM) ethers either on the phenolic -OH or on the benzylic -OH and reacting the other -OH group with bromoacetaldehyde dimethyl acetal, followed by treatment with BF3-OEt2 (Scheme 9) <2004T11453>. 

Toluenesulfonic acid Bromoacetaldehyde diethyl acetal Sodium periodate Hexamethyldisilazane... 

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