Phthalide enolates

Phthalide enolates 4 add to Schiff bases to produce intermediate adducts 5 which cyclize to mixtures of cis- and Rcws-isoquinolones 6 and 724. The er.y-product predominates consistently by — 2 1 over a series of nonenolizable arylintines. 

The preference for the civ-isomer has been explained by a cyclic transition state in which the steric interactions of the a-substituent of the iminc arc minimized by placing it gauche to the lactone. 8 shows the proposed transition state involved in the addition of phthalide enolates to imines24. 

The addition of lithium alkoxydienolates to a,P-enones occurs exclusively in the l,4(a)-mode. For example, alkoxydienolate (202), obtained from ethyl senecioate, adds efficiently, in a tandem conjugate addition-allylation protocol, to cyclopentenone to afford the a,(3-functionalized cyclopentanone (203),153 In contrast, the lithium dienolate (204), from 5-methylbutenolide, affords exclusive y-alkylation,154 b while the analogous phthalide enolates (206) can be exploited to accomplish regiospecific polynuclear aromatic syntheses (Scheme 76).l54c ... 

Phthalide enolates (145), which can be viewed as dihomoenolates, add to Schiff bases to produce intermediate adducts (146) that cyclize to mixtures of cis and trans 3-aryl-4-hydroxy-3,4-dihydro-l(2W)-isoquinolones (147) and (148) (Scheme 30). As originally described by Dodsworth, Sammes and... 

Figure 6 Proposed transition state involved in the addition of phthalide enolates to imines ...

In connection with the synthesis of protoberberine alkaloids, Marsden and MacLean have investigated the addition of phthalide enolates to 3,4-dihydroisoquinolines. These reactions are an extension of the previously described work of Dodsworth et involving phthalide additions to acyclic imines... 

Figure 9 Proposed orientation of reactants in phthalide enolate-imine additions leading to (a) cis or (b) trans...

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