3 -Isoquinolinones reduction

Volume 75 concludes with six procedures for the preparation of valuable building blocks. The first, 6,7-DIHYDROCYCLOPENTA-l,3-DIOXIN-5(4H)-ONE, serves as an effective /3-keto vinyl cation equivalent when subjected to reductive and alkylative 1,3-carbonyl transpositions. 3-CYCLOPENTENE-l-CARBOXYLIC ACID, the second procedure in this series, is prepared via the reaction of dimethyl malonate and cis-l,4-dichloro-2-butene, followed by hydrolysis and decarboxylation. The use of tetrahaloarenes as diaryne equivalents for the potential construction of molecular belts, collars, and strips is demonstrated with the preparation of anti- and syn-l,4,5,8-TETRAHYDROANTHRACENE 1,4 5,8-DIEPOXIDES. Also of potential interest to the organic materials community is 8,8-DICYANOHEPTAFULVENE, prepared by the condensation of cycloheptatrienylium tetrafluoroborate with bromomalononitrile. The preparation of 2-PHENYL-l-PYRROLINE, an important heterocycle for the synthesis of a variety of alkaloids and pyrroloisoquinoline antidepressants, illustrates the utility of the inexpensive N-vinylpyrrolidin-2-one as an effective 3-aminopropyl carbanion equivalent. The final preparation in Volume 75, cis-4a(S), 8a(R)-PERHYDRO-6(2H)-ISOQUINOLINONES, il lustrates the conversion of quinine via oxidative degradation to meroquinene esters that are subsequently cyclized to N-acylated cis-perhydroisoquinolones and as such represent attractive building blocks now readily available in the pool of chiral substrates. 

The photostimulated reactions with the enolate anions of 1-indanone and a-tetra-lone lead to the reduction product benzamide (23% and 44%, respectively), together with the target fused isoquinolinones (51% and 42%, respectively) [65]. The formation of benzamide can probably be ascribed to the hydrogen atom abstraction from the cyclic ketone. 

The intramolecular Friedel-Crafts cyclisation of N-2-naphthylalkylalanines proceeds with retention of configuration and subsequent reduction of the resulting isoquinolinone provides a stereospecific synthesis of the diastereoisomeric 1,2,3,4-tetrahydrobenzo[f]isoquinolin-1-ols (93 and 94) (E. Gellert, N. Kumar and D. Tober,... 

Under ruthenium-catalyzed ortho-C-H activation and intramolecular C-N bond formation, the condensation of iminophosphoranes (in situ generated from acyl azides and triphenylphosphine) with internal alkynes afforded a variety of isoquinolinone derivatives (Eq. (7.43)) [53]. The regioselective insertion of unsymmetrical alkynes led to an (aryl)C-N bond formation. Thiophene and indole-based acyl azides were also compatible for this transformation. A domino reaction sequence via coordination of ruthenium with Af-atom of iminophosphoranes, ort/zo-cyclometalation, alkyne insertion, protonation, and reductive elimination was proposed for the catalytic cycle. Based on and NMR experiments, the involvement of benzamide during the reaction process was ruled out. 

---