A new approach to synthesis of 3,3‐dialkyl‐3,4‐dihydroisoquinoline derivatives

Abstract

The synthesis of 3,3-dialkyl-3,4-dihydroisoquinolines via heterocyclization in threecomponent reaction of an activated arene with isobutyraldehyde and nitriles is described.

Neospiroenones. Synthesis of 10,11-dimethoxy-1,6,6-trimethyl-5,6,8,12b-tetrahydrobenzo[d,f]indol-4(3H)-one and 10,11-dimethoxy-6,6-dimethyl- 1,5,6,12b-tetrahydrobenzo[d,f]indol-2(8H)-one

“…Then the product was filtered off, dried, and purified by chromatography (chloroform-acetone (12)). 13 X ray diffraction study of compound 5. Single crystals of com pound 5 were obtained by the crystallization from ethyl acetate.…”

Aliphatic aldehydes in the synthesis of carbo- and heterocycles: Part II. Synthesis of six- and seven-membered rings, bicyclic compounds, and macrocycles

“…Therefore, to obtain 3-monosubstituted isoquinolines, the reaction center should be localized on α-unbranched aldehyde. However, analogous reaction of propionaldehyde (1a) with 1,2-dimethoxybenzene in the presence of sulfuric acid gave 2,3,6,7-tetramethoxy-9,10-diethylanthracene (69) as the only product [73,74] (Scheme 18). Presumably, intermediate diarylmethane 70 undergoes secondary attack by protonated propionaldehyde and subsequent oxidation to compound 69.…”

“…The use of isobutyraldehyde instead of isobutylene oxide as twocarbon synthon in the Ritter reaction ensures easy preparation of 3,4-dihydroisoquinoline derivatives not only from dimethoxybenzenes but also from o-and p-xylenes. This makes the three-component synthesis from arene 64, nitrile 65, and isobutyraldehyde (1e) more attractive [73][74][75][76] (Scheme 17). The products were previously unknown dihydroisoquinolines 66.…”

Direct heterocyclization of benzocrown ethers

“…We continue our studies of 3,3-dialkyl-3,4-dihydroisoquinolines [7,8], and here we report the synthesis of some novel benzocrown ether derivatives.…”