A highly stereoselective synthesis of 3,4-dihydro-1(2H)-isoquinolinones and 8-oxoberbines from homophthalic anhydrides and azomethines

Synthesis and a Configurational Correlation within cis- and trans- Oxazolotetrahydroisoquinolinones with an Angular Substituent

“…The reaction of homophthalic anhydride (2) and two different oxazolines proceeded in the expected manner [11] with retention of the angular substituent, but with different diastereoselectivity. Thus, equimolar quantities of homophthalic anhydride (2) and 2-phenyl-2-oxazoline (3) gave in the presence of benzene at reflux only one product, identified [9] as acid 4 with an assumed trans-configuration (Scheme 1).…”

Synthesis of New trans-2-Benzyl-3-(furan-2-yl)-4-substituted-1,2,3,4-tetrahydroisoquinolinones

“…By analogy to Refs. [15] and [17], a trans configuration was attributed to the isomer with the smaller J 3,4 (0 Hz) and a cis configuration to the one with the greater J 3,4 (5.75 Hz).…”

“…The ratios between trans-5, cis-5 and 6 in the acid products were determined by 1 H-NMR spectroscopy from the integrals of relevant protons and are shown in Table 1. The signals for the protons at C-3 (5.07 ppm for cis-5 and 5.29 ppm for trans-5) and at C-4 (4.64 ppm for cis-5 and 4.24 ppm for trans-5) were used for 5 [15,17]. In the case of product 6 the methylene protons (3.92 ppm) were taken into account.…”

“…Several methods have been described for preparation of tetrahydroisoquinolines [7][8][9][10][11][12][13][14][15][16][17][18][19][20]. The reaction between homophthalic anhydride and imines, developed in our laboratory [15], is nowadays a well known method for an one step preparation of acids of type 1 having two stereogenic centers and thus cis and trans forms if R 1 is different from R 2 [15][16][17][18][20][21][22].…”

“…Depending of the conditions (solvent, temperature and catalyst if any), the reaction leads to mixtures of cis-and trans-isomers or to one of these isomers [15][16][17][18][21][22][23][24][25][26]. In some cases side reactions take place and by-products are isolated [20][21][22].…”