Addition of o-iodobenzoyl chlorides to imines affords Nacyliminium ions, perhaps in equilibrium with a-chlorobenzamides, as adducts. Reaction of the adducts with 1.1 equivalents of phenyllithium at -78 °C followed by warming to ambient temperature induces an intramolecular Wurtz-Fittig coupling to afford 2,3-dihydroisoindolones in excellent yields.The reaction of acid chlorides with imines affords adducts 3 which may be represented formally as the N-acyliminium ions 3a or the corresponding a-chloroamides 3b derived from 1,2-addition across the imine C-N bond. 1 Such adducts of imines and a variety of acylating agents, which include acid chlorides and anhydrides, have been proposed as intermediates in the synthesis of a number of different heterocycles. 2 This has included several complex natural products containing heterocycles as substructures. 3 Reaction of acid chlorides with simple imines has also been used in a method to protect a secondary amide. 4 Our interest in preparing isoindolones prompted speculation that adducts 3 derived from the addition of o-iodobenzoyl chlorides to imines might be readily cyclized under reductive coupling conditions to afford 2,3-dihydroisoindolon-1-ones (Scheme 1). Thus, generation of an anion or anion equivalent ortho to the benzoyl carbonyl group in the benzoyl chloride/imine adduct 3 should provide an intermediate poised to cyclize to an isoindolone. 5 We proposed that the desired cyclization might be induced by forming the ortho-lithio derivative 4 from the oiodobenzoyl chloride/imine adduct 3, by lithium-iodide exchange. 6 Such a reaction would be similar in principle, to the Wurtz-Fittig-type cyclization of a,w-dihaloalkanes induced by tert-butyllithium, which was described by Bailey and co-workers. 7 We were also encouraged by our previous work utilizing lithium-iodide exchange to generate internally functionalized aryllithium reagents, in the presence of imines, as method to prepare isoindolones. 8 Direct nucleophilic couplings to form a bond between the carbon a to nitrogen and the ortho-C-aryl carbon to form an isoindolone ring are rare (5, formation of red bond). 9Scheme 1 (a) Addition of acid chlorides to imines to form N-acyliminium salts 3a and/or chloroamides 3b; (b) lithium-iodide exchange-induced cyclization to form isoindolone 5 A representative adduct 3 was prepared by adding o-iodobenzoyl chloride to a THF solution of butylidenebutylamine 2, (R 1 = Pr, R 2 = Bu, R 3 = H) at -25 °C. After stirring for 10 minutes at -25 °C, the resulting solution was cooled to -78 °C and phenyllithium (1.1 equivalent) was added dropwise. The cooling bath was removed immediately, and the mixture was warmed to ambient temperature. Isoindolone 5 (R 1 = Pr, R 2 = Bu, R 3 = H) was isolated in a 90% yield. The reaction was very clean, with only a minor amount of a single by-product being detected. The by-product was identified as N-[(1E)-1-butenyl]-N-butylbenzamide, presumably arising from some minor competing b-elimination from the acid chloride/imine adduct 3 (R 1 = Pr, R 2 = Bu,...