Phthalides and derivatives are widespread in biologically active compounds and natural products. These heterocycles can also serve as versatile building blocks for the synthesis of natural and pharmaceutically-important products. Their preparation is widely documented in the literature even though many of their synthetic routes are non-convergent and relied on intramolecular cyclization, requiring relatively complex syntheses of the starting materials in order to bring diversity to the final phthalides. Moreover, fused heteroaryl-lactones (pyridinyland benzothienyl-) are poorly exemplified in the literature. In the past few years, our laboratory has been focusing on developing chemistry using bimetallic ate complexes composed of a polar organometallic and a “soft” organometallic in metal halogen exchange (MHE) reaction. Based on that expertise, we decided to started a research program with the aim of exploring the reactivity of organomagnesiates for the synthesis of substituted phthalides, azaphthalides and also fused benzothienyl-lactones. Thereby, we showed that BIPHEN or BINOL-based monobutylmagnesiate ((rac)- BIPHENBuMgLi or (rac)-BINOLBuMgLi) can efficiently promote the MHE of easily available 2-iodobenzoate derivatives, followed by addition of an aldehyde or a ketone which lead to an intramolecular cyclisation, and the formation of a series of new diversely substituted phthalide derivatives in moderate to good yield.