1 -Benzyl-2,4-dimethyl-5-formyl

Isoindole, l-benzyl-3-formyl-, 4, 222 Isoindole, 1-cyano-synthesis, 4, 148 Isoindole, 2-cyano-synthesis, 4, 149 Isoindole, 1,3-dimethyl-... 

I, 4- and 3,4-Dihydroquinazolines are tautomeric but any attempts to prepare the former w ithout a 1-substituent have led to the latter. The greater stability to proto tropic change of 1,2-dihydronaphthalene over 1,4-dihydronaphthalene is also found in 3,4-dihydroquinazoline. Earlier claims to the preparation of l,4-dihydroquinazolines ° were erroneous and based on incomplete experimental data. The first 1,4-dihydroquinazoline was prepared as recently as 1961. 1-Methyl and l-benzyl-l,4-dihydroquinazolines were obtained from o-methylamino-and o-benzylamino-benzylamines (42) by formylation and ring closure. Attempts to remove the benzyl group gave 3,4-dihydroquinazoline. These 1,4-dihydro compounds are susceptible to oxidation, and attempts made to prepare 1,2-dimethyl-1,4-dihydroquinazoline from o-... 

Dimethylamino-methyl)-2-hydroxymethyl-aus 2 -Carboxy-2-(dimethylaminocarbonyl)-biphenyl und Lithiumalanat 165 2,2 -Dinitro- 474, 476, 695 6,6 -Dinitro-2,2 -bis-[chlorcarbonyl]- 188 2,2 -Dinitro-4,4 -bis-[diathylamino]- 695 4,4 -Dinitro-2,2 -bis-rhydroxymethyl]- 213 6,6 -Dinitro-2,2 -bis-[hydroxymethyl]- 188 2,2 -Dinitro-4,4 -diamino- 695 6,6 -Dinitro-2,2 -diformyl- 694 4,4 -Dinitro-2,2 -dimethoxycarbonyl- 213 2,2 -Dinitro-4,4 -dimethyl- 695 6,6 -Dinitro-2 -formyl-2-carboxy- 694 2,2 -Dinitroso- 476 -4-hydroxamsaure-chlorid 537 4-(a-Hydroxy-benzyl)- 542 Methoxy- 678 2-Methyl- 556 Nitro- 672, 678 4-Nitro- 687... 

Dihydro-2(l,3-dimethyluracil-5-yl)-l,3,4-oxadiazole was obtained in 53% yield by the [3+2] cycloaddition of diazomethane to the formyl group of l,3-dimethyl-5-formyluracil <1997T7045>. The reaction of l-acetyl-2-benzyl-hydrazine with methyl glyoxalate in toluene afforded an oxadiazolidine derivative <1996TL4323>. 

Abbreviations Standard abbreviations as recommended by IUPAC-1UB Commission are used in this review (1). Other abbreviations include Acm, acetamidomethyl Bn, benzyl Boc t-butyloxycarbonyl Bom, benzyloxymethyl BHA, benzhydrylamine Cbz, benzyloxycarbonyl cHx, cyclohexyl DCC, N,N-dicyclohexylcarbodiimide DCM, dichloromethane Die, N,N-diisopropylcarbodiimide DMF, N,N-dimethylformamide DMSO, dimethyl sulphoxide For, formyl Fmoc, 9-fluorenylmethyloxycarbonyl HMP, 4-hydroxymethylphenoxyacetyl HOAt,... 

A derivative of a hitherto unknown nucleus was produced when 4-amino-5-aminomethyl-3-methyltriazole was refluxed with carbon disulfide and triethylamine in pyridine, which yielded 3-methyl-3,7-dihydro-l,2,3-triazolo-[4,5-d][l,3]thiazine-5-thione (98) (3 hr, 53%) the 3-benzyl analog was made similarly (63%) [80JCS(P1)2009]. Cyclization of 4-anilino-5-ethoxycarbonyltriazole with polyphosphoric acid produced 1 f/-triazolo-[4,5-h]quinol-4-one (99) [80EUP(A)2562]. Similarly, ring closure of 4-(2-pyridylamino)triazole-5-carboxylic acid (or its esters) gave l//-pyrido-[l,2-a]-l,2,3-triazolo[4,5-d]pyrimidin-4-one (100) (77GEP2757929). 4-Amino-5-formyl-3-methyltriazole and pentane-2,4-dione, set aside in 20% sulfuric acid, yielded 3,5-dimethyl-3//-l,2,3-triazolo [4,5-6] pyridin-6-yl... 

Dihydroxycoumarin (55) underwent selective methylation (dimethyl sulfate) to the 7-methoxy derivative (56), which upon benzylation and oxidation (selenium dioxide), afforded the 4-formyl coumarin (74). Conversion to the acetal (75) occured upon treatment with triethyl orthoformate, and subsequent catalytic hydrogenation served the dual purpose of removal of the benzyl group and reduction of the coumarin double bond, to give (76). Hydride reduction of the derived acetate (77), followed by acidic workup, gave directly the furobenzofiiran (75) [presumably through the hydroxy aldehyde (75)]. Comparison of the spectra of racemic (75) with those of the naturally derived material showed the compounds to be identical. 

Benzyl-piperazino)-6-cyano- - 914 3-Bromo-6-chloro-6-methyl- - 1459 3-Bromo-6-chloro-6-methyl- -4,5-dimethyl- 1459 6-Cyano-6-morpholino- - 908 6-Cyano-6-piperidino- - 908 - -4,5-diphenyl- 278 1-Ethinyl- -4,5-dimethyl- 1786 1-Formyl- -4,5-dimethyl- 1786 1-Hydroxymethyl- -4,5-dimethyl- 294... 

In the still more 7t-deficient 1,2,3-triazole series (see 20), several 4-amino-5-formyl derivatives resisted both direct acylation and acetal formation. A successful alternative was to form intermediates with side chains conjugated to the nucleus. For example, 1- and 2-methyl-, as well as 3-benzyl-4-amino-l,2,3-triazole-5-aldehydes reacted with a cold mixture of dimethylformamide and phosphoryl chloride to give excellent yields of, e.g., 3-benzyl-4-dimethyl-aminomethyleneamino-l,2,3-triazole-5-aldehyde (84). This was converted to 9-benzyl-8-azapurine (see 21) in excellent yield by refluxing in methanolic ammonium acetate.87 In a variation of this reaction, an imidate (85) replaced the amidine (84) as intermediate. Thus, 4-amino-l-methyl-l,2,3-triazole-5-aldehyde and triethyl orthoacetate, refluxed for 2 hr, gave an excellent yield of 4-ethoxyethylideneamino-l,2,3-triazole-5-aldehyde (85), cyclized, by stirring in cold ethanolic ammonia, to 2,7-dimethyl-8-azapurine (good yield).87... 

Aromatic cyclodehydration has been used in the preparation of several indolo[2,3-a]acridizinium salts (43) (Chart V). Reaction of l-formyl-)3-carboline (LXIX) with benzyl bromides in dimethyl formamide at room temperature provided the quaternary salts (LXX R = H or OMe) which were smoothly converted to the desired indolo-[2,3-a]acridizinium salts (LXXI) by action of polyphosphoric or concentrated hydrochloric acid (when R = OMe). 

Condensation of syn- or anti-27 with hydrazine afforded new pyrazole derivatives 28 with a stereodefined and protected amino diol side chain [64]. The preparation of push-pull substituted unsaturated monosaccharide derivatives and their use in the synthesis of nucleoside analogs have been reviewed [65]. Thus, the 2-formyl pentose glycals were transformed to the corresponding acyclo-C-nucleosides 29 [66]. Similarly, the benzy-lated 2-formylglycals reacted with hydrazine derivatives to afford the substituted l,2,4-tri-0-benzyl-lC-(lH-pyrazol-4-yl)-D-tetritols the deprotection of which was achieved with Pd/H2 to yield the lC-( 1-methyl-lH-pyrazol-4-yl)-D-tetritols [67]. 3-0-Benzyl-6-deoxy-l,2-0-isopropylidene-o -D-xylo-hept-5-ulofuranurono-nitrile was reacted with f, N-dimethylformamide dimethyl-acetal in THF to furnish the (E)-3-0-benzyl-6-deoxy-6-dimethyl-aminometh-ylene-l,2-0-isopropylidene-Q -D-xylo-hept-5-ulofuranurono-nitrile as a major product, and on treatment with carbon disulfide and methyl iodide under basic conditions afforded 3-0-benzyl-6-deoxy-l,2-0-isopropylidene-6-[bis(methylsulfanyl)methylene]-a-D-xylo-hept-5-ulofuranurono-nitrile. Further reaction with hydrazines yielded the reversed pyrazole-C-nucleoside analogs [68]. 

The synthesis pathway started with the lithiation of ethylbenzene 121 at the benzylic position, followed by acylation of the toluate anirni intermediate at low temperature. It is noteworthy that a potentially competing orf/io-lithiati(Mi of the type championed by Snieckus 85) i.e. between the two stabilizing methoxyl radicals) was not reported under these conditions. Subsequent reduction of benzyUcetone 122 provided smooth access to the t/irco-dimethyl-substituted bicy-clic intermediate 123 via lactonization. DIBAL reduction (—> 124) and reductive debenzylation with palladium on charcoal gave the ring-opened alcohol 125, which was further demethylated to provide a 1,3-diphenol, and then carboxylated under buffered conditions to yield acid 117, also known as phenol B . This compound was formylated with trimethyl orthoformate and acid, then cyclized to give the quinone structure and natural product, 116 (Scheme 3.1). 

K-tert-butoxide added at ca. 10° to a soln. of 2-formyl-4,5-dimethoxy-N-p-nitro-benzyl-N-benzoyl-/ -phenylethylamine in dimethyl sulfoxide, shaken 5 min., and the product isolated the next day -> 2,3-dihydro-3-benzoyl-4-p-nitrophenyl-7,8-dimethoxy-lH-3-benzazepine. Y 93%. F. e. s. M. Shamma and L. Toke, Tetrahedron 31, 1991 (1975). 

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