Direct couplings of the cY-bromomethylacrylates and the doubly charged succinate ion are described. For a number of years we have been interested in the development of new annulation which would afford five-membered rings via direct coupling of the fl-haloesters and the doubly charged succinate ions. 1 Conceptually, this approach should result in the one-pot construction of cyclopentanones with a " variety of side chains at the desired positions .d The obvious drawback of the methodology is the lack of regio-and stereoselectivities, 3 and an attractive solution to this problem is reported in this and the following papers. The readily available diisopropyl suceinate (l_)4 in dry tetrahydrofuran (THF), on exposure at -78°C with 2.1 equiv of lithium diisopropylamide (LDA) for 1 h, undergoes facile metallation to give a pale yellow solution of the dianion 2; treatment of this solution at -78°C for 20 min with 1 equiv of ethyl (Y-(bromomethyl)acrylate in hexamethylphosphoric triamide (HMPA) gave on aqueous work-up and chromatography on silica gel5 the cyclopentanone 3" in 56%~ yield. Attention was then turned to the application of the method to annulation which was simply effected by reaction of 2 with the olefinic bromoester 4: reaction in THF-HMPA at -78°C for 1 h and 0°C for 1 h, followed by usual work-up gave the bicyclic ketone 57 in 88% yield. The preparation of L was readily accomplished from ethyl 2-oxocycloheptanecarboxylate in three steps: (1) hydrogenation (PtO2, 88%);8 (2) selenation (LDA, PhSeBr)-deselenation (H202) sequence (58%); 9 (3) bromination (PBr3, 95%).