PubMed Health⌕ Search

Biomedical subjects

Alan R. Katritzky

Publications and source records attributed to Alan R. Katritzky.

At least 19 recordsLinked to original sources
PubMed1999

Synthesis of Substituted Piperidines from N,N-Bis[(benzotriazol-1-yl)methyl]amines.

N,N-Bis[(benzotriazol-1-yl)methyl]benzylamines and N,N-bis[(benzotriazol-1-yl)methyl](p-N',N'-dimethylphenyl)amine on reaction with allyltrimethylsilanes yielded substituted piperidines. Other N,N-bis[(benzotriazol-1-yl)methyl]anilines (unsubstituted and p-CH(3), OCH(3), Cl) gave julolidines (2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij] quinoline).

Journal Article↗
PubMed1999

Asymmetric Syntheses of 2-Substituted and 2,5-Disubstituted Pyrrolidines from (3S,5R,7aR)-5-(Benzotriazol-1-yl)-3-phenyl[2,1-b]oxazolopyrrolidine.

Benzotriazole, 2,5-dimethoxytetrahydrofuran, and (S)-phenylglycinol in one step gave 80% of (3S, 5R,7aR)-5-(benzotriazol-1-yl)-3-phenyl-[2,1-b]oxazolopyrrolidine (6), whose crystal structure was confirmed by X-ray crystallography. Novel chiral pyrrolidine synthon 6 reacts with organosilicon (allyltrimethylsilanes and vinyloxytrimethylsilanes), organophosphorus, organozinc, and Grignard reagents to afford chiral 2-substituted and 2,5-disubstituted pyrrolidines.

Journal Article↗
PubMed1997

Preparations of Trisubstituted Hydrazines and Pyrazolidines from N-(1-Benzotriazolylalkyl)hydrazines.

Reactions of N,N'-disubstituted hydrazines with benzotriazole and aldehydes give N-(alpha-benzotriazoylalkyl)-N,N'-disubstituted hydrazines which on treatment with organometallic reagents form N-alkyl-N,N'-disubstituted hydrazines in good yields. N-(Benzotriazolylalkyl)-N,N'-disubstituted hydrazines and electron-rich olefins, in the presence of zinc bromide catalyst, generate N,N'-disubstituted pyrazolidines in moderate to good yields.

Journal Article↗
PubMed1997

General Synthesis of Polysubstituted Benzo[b]furans.

2-(Benzotriazol-1-ylmethyl)furans 4a-c, on treatment with n-BuLi followed by various alpha,beta-unsaturated ketones and aldehydes, gave the adducts 6a-f which underwent intramolecular cyclization to form substituted benzo[b]furans 10a-f. Lithiation and subsequent alkylation of 4a-c afforded intermediates 8a-c, which underwent similar transformations with alpha,beta-unsaturated ketones or aldehydes to give the corresponding polysubstituted benzo[b]furans 7a-c. o-Iodophenol (11) with 1-propargylbenzotriazole (1) in the presence of (PPh(3))(2)PdCl(2), CuI, and Et(3)N gave 2-(benzotriazol-1-ylmethyl)benzo[b]furan (12). The benzotriazolyl-CH(2) side chain of 12 was further elaborated by (i) alkylation with trans-cinnamaldehyde to give the adduct 14, followed by intramolecular cyclization to give dibenzofuran 17; (ii) alkylation with benzyl bromide followed by elimination or nucleophilic displacement of the benzotriazolyl moiety with Grignard reagent and subsequent dehydrogenation to give 2-alkenylbenzofurans 15 or 20, respectively; (iii) alkylation with (CH(3))(3)CCHO followed by low-valent titanium-promoted olefination to give olefin 19; and (iv) alkylation with benzaldehyde followed by Lewis acid catalyzed pinacol type reaction to give 18.

Journal Article↗
PubMed1997

Benzotriazole-Mediated Conversions of para-H-Substituted Pyrylium, Benzo[b]pyrylium, and Xanthylium Salts into para-Position Functionalized Derivatives (An Indirect Electrophilic Substitution of Electron-Deficient Heteroaromatics).

4H-Substituted pyrylium 9, benzo[b]pyrylium 15, and xanthylium salts 22 react with benzotriazole to give the corresponding 4H-(benzotriazol-1-yl)pyrans 10, benzo[b]pyrans 16, or xanthenes 23. Novel anion precursors 10, 16, and 23 undergo smooth lithiations at the positions alpha to the benzotriazol-1-yl function, i.e., at the para-position of the O-heterocycle. Subsequent trapping with different alkyl halides gives intermediates 14, 21, and 25, which are converted by mineral acid into para-functionalized pyrylium 11-13, benzo[b]pyrylium 17-20, and the xanthylium 24 salts in good to excellent yields.

Journal Article↗
PubMed1997

Palladium-Catalyzed Cross-Coupling Syntheses of Benzotriazolyl Enynes and a General Route to Enynyl Ketones and Alkynyl Ketones.

A new general route to conjugated enynyl ketones was developed based on a two-step procedure. First, palladium-catalyzed cross-coupling reactions of 1-(benzotriazol-1-yl)propargyl ethyl ether (3) and vinyl triflates or vinyl bromides afforded the key intermediates [1-(benzotriazol-1-yl)-1-enynyl]methyl ethyl ethers 5a-d in good yields. Then reactions of compounds 5 with primary halides gave intermediates 8, which were hydrolyzed by dilute acid to enynyl ketones 9a-g. Similar palladium-catalyzed coupling reactions of 3 with various aryl iodides followed by an analogous sequence afforded aryl-substituted propargyl ethers 12a-d and thence alkynyl ketones 13a,b.

Journal Article↗
PubMed1997

Lewis Acid-Catalyzed Additions of (Benzotriazol-1-yl)diethoxymethane to Enol Ethers and Enamides. New Syntheses of beta-Alkoxyalkanal and beta-Aminoalkanal Acetals.

Addition of (benzotriazol-1-yl)diethoxymethane 11 to various acyclic and cyclic enol ethers and enamides produces the corresponding adducts, which were reacted with either NaAlH(4) or Grignard reagents to afford acyclic acetal-ethers (18a-f), cyclic alpha-(substituted)-beta-acetals (19a-c), amino-acetals (24a,b), and 1,3-amino-ethers (25), all known but previously difficult-to-access classes of compounds.

Journal Article↗
PubMed1997

Benzotriazole- and 1,2,4-Triazole-Stabilized Allylic Anions: Applications in Syntheses of Functionalized alpha,beta-Unsaturated Ketones, gamma-Lactones, gamma-Lactams, and beta-Substituted Esters.

Deprotonated 1-(benzotriazol-1-yl)-1-ethoxy-2-hexene (7) reacted with alkyl halides, aldehydes, ketones, imines, and alpha,beta-unsaturated esters to give exclusively the alpha-alkylated products 8a-c, 10a,b, 12, 14, 16, and 18a,b, respectively. Without isolation, these products were hydrolyzed under mild conditions to generate the corresponding simple or functionalized alpha,beta-unsaturated ketones 9a-c, 11a,b, 13, 15, 17, and 19a,b. Similar reactions with the phenyl-substituted analog 3-(benzotriazol-1-yl)-3-ethoxy-1-phenyl-1-propene (21) also gave the analogous alpha-products, but they were accompanied by small amount of the gamma-products in most cases. By contrast, deprotonation of the corresponding triazole derivative 29 with butyllithium followed by reactions with alkyl halides, aldehydes, ketones, or imines yielded exclusively gamma-alkylated adducts 32, 34, 36, 38, 40, and 42. Intermediates 32, 34, 36, 38, 40, and 42 were readily converted into beta-substituted esters 33a-c, gamma-lactones 35a,b, 39, 41, and 43, and gamma-lactams 37a-c on hydrolysis.

Journal Article↗
PubMed1997

Novel Syntheses of alpha,beta-Unsaturated Esters, alpha,beta-Unsaturated gamma-Lactones, and 2-Alkoxypyrroles via 1,2,4-Triazole-Stabilized Allenic Anions.

The dianion 12 (right harpoon over left harpoon 13) of 1-(1,2,4-triazol-1-yl)phenylpropargyl ethyl ether 11(readily prepared from phenylpropargylaldehyde diethyl acetal 8 and 1,2,4-triazole) reacts with alkyl halides, aldehydes, ketones, and alpha,beta-unsaturated ketones to give exclusively gamma-substituted allenic products of type 10. These adducts underwent mild in situ hydrolysis enabling convenient syntheses of alpha,beta-unsaturated esters 9a-c and alpha,beta-unsaturated gamma-lactones 16, 18, 20, and 22. Reactions of dianion 13 with imines generated the 1,3,4-trisubstituted 2-alkoxypyrroles 27, 30, and 31 in high yields. The alkyl-substituted analog 34 underwent similar reactions to give predominantly the gamma-products 39,40, and 42 along with a small proportion of alpha-analogs.

Journal Article↗
PubMed1997

Benzotriazole-Assisted Aromatic Ring Annulation: Efficient and General Syntheses of Polysubstituted Naphthalenes and Phenanthrenes.

(Benzotriazol-1-ylmethyl)benzenes and -naphthalenes 1a-f, easily accessible from benzyl bromides and benzotriazole, readily undergo lithiation and subsequent 1,4-addition to alpha,beta-unsaturated aldehydes and ketones. Intramolecular cyclization of the products, induced by acetic acid-hydrobromic acid or polyphosphoric acid (PPA), followed by simultaneous dehydration and debenzotriazolylation furnishes a wide range of polysubstituted naphthalenes 7a-f and of phenanthrenes 9 and 11 in moderate to good yields in one-pot procedures. If compounds 1 are first lithiated and reacted with electrophiles, the resulting alkylation products undergo similar annulation reactions with alpha,beta-unsaturated carbonyl compounds to provide the more highly substituted naphthalenes 6a,b and phenanthrenes 10a,b in moderate overall yields.

Journal Article↗