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2.4.5.2 Variation 2: Via Nucleophilic Substitution

DOI: 10.1055/sos-SD-002-00214

Kündig, E. P.; Pache, S. H.Science of Synthesis, (20032168.

The electrophilic tricarbonylchromium group activates the arene ring toward nucleophilic attack. Chlorobenzene complexes readily undergo SNAr substitution of chloride by hydroxide, alkoxide (e.g., 34 35, 39 40),[‌110‌] phenoxide (e.g., 38 39),[‌111‌] and thiolate nucleophiles as well as by sodium hydride/trifluoroacetamide (e.g., 36 37) (Scheme 8).[‌112‌] The reaction is particularly efficient under phase-transfer conditions, in benzene in the presence of crown ethers, or in dimethyl sulfoxide. In contrast, more reactive carb­anions preferentially add ortho to the chlorobenzene complex 6 (M=Cr; R1=Cl) and ipso substitution is feasible only for nucleophiles that add reversibly. The fluoro complex 6 (M=Cr; R1=F) is even more reactive: in dimethyl sulfoxide, fluoride is substituted by a wide range of nucleophiles that include alkoxides, carboxylates, amines, and a variety of carbanions ranging from acetylides to ketone enolates.[‌113‌,‌114‌] An example of an intramolecular reaction is shown by the transformation 41 42.[‌115‌]

Meeeee 8 eeee Meeeeeeeeeee Meeeeeeeeeee[‌888‌‌888‌,‌888‌]

Me eeeeeeeeeee eeeeeeee eee ee eeeeeeee eeeeeeeeeeee ee e eeeeee, e eeeeeeeee, ee eeee e eeeeeeeee eeeeeeee ee e eeeeeeee ee eeeeeeeeeee eeeeeeee, eeeeeeeeeee, eee eeeeeeeeeee (Meeeee 8).[‌888‌‌888‌] Meeeeeeee ee eee eeeeeeeeeeeeeeee ee eeeeeeeeeee eeeeeeee, eee eeeeee ee eee eeeeeeee ee e eeee eeeeeeeeeeee (eeeeeeeeeee eeeeeeee eeeee ee eee eeeeeee eeeee) ee eeee eeeeeeeeeeee (eeeeeeeeeee eeeeeeee eeee ee eeee ee eee eeeeeee eeeee) (e.e., 88 88). Meeeeeee eee eeee eeeeeeeee eeeee eeee 8M eeeeeeee ee eee eeeeeeee eeeeeee. Meeeee ee eeeee eeeeeeeee eee ee eee, eeeeeee ee eeeeeeeeeee eeeeeeeeeeeeee ee eeeeee eee eeeee eeeeeee ee eee eeeeeee eeeeeeeeeeeeeee, eeeeee, eeeeeee eeeeeeeeeeeeee eeeeeee.[‌888‌,‌888‌]

Meeeee 8 eeee Meeeeeeeeeee Meeeeeeeeeee[‌888‌‌888‌]

Mee eeeee eeeeeeeeeeeee eeee ee eeeeee eee eeeeeeeeeee ee e eeeeeee eeeee ee eee eeeee, eeeee eeeeeeeeeeee eeeeeeeeeeee ee eeeeeeee eeeeeeee ee eeeeeeeeeee. Meee eee eeeeeeee eeee eeeeeeee, eeeeee ee e eeeeeeee eeeeeee: eeeee eeeeeeeeeeee eeeeeeee ee eeeeeeeeeeeee eeeeeeeee ee eeeeeee 88, eeeeeeee ee ee eeee eeeeeee eeeeeeeeeee, eeeee eee eeeee-eeeeeeeeeee eeeee eeeeeeeee 88 (Meeeee 88).[‌888‌] Mee eeeeeee ee eee eeee-eeeeeee ee 88 ee eee eeeeee eeeeee ee eeeeeee ee ee eeeeeeeeeee ee eeeeeeeeeeeeeee ee eee Meeee eeee ee eee eeeeeeee eeee eeee. Meeeeeeee 8 eee 88 eeeee eeeeeeeee. Meeeeeeee- eee eeeeeeeeeeeeeeee eeeeeeee eeee eeee eeeeeeee (eee Meeeeee 8.8.8.8).

Meeeee 88 Meeeeeeeeee MeeeeeeeMeeeeee Meeeeeeeeee[‌888‌]

Meeeeeeeeeee Meeeeeeee

Meeeeeeeeee(η8-8-eeeeeeeeeeeeeeeeeeee)eeeeeeee(8) [88, M8=MM(Me)MM]:[‌888‌]

Me e eeee ee eMe8MM (8.8eM, 88.8eeee) ee MMM (88eM) ee 88°M eee eeeee 8.88M MeMe ee eeeeee (8.8eM, 88.8eeee). Mee eeeeeee eee eeeeee ee 8°M eee 88eee eee eeee eeeeee eeeee ee 88°M. Meeeeeeeeeeeee (8.88eM, 88.8eeee) eee eeeee eee, eeeee 88eee, [Me(MM)8(η8-eeeeeeee eeeee)] (88; 8.88e, 88eeee) eee eeeee ee e eeeee. Meeee eeeeeee ee ee eeeeeeeee, eee eeee eee eeeeeeeee eeee Me8M, eeeeee eeee 8% ee MMe, 8% ee MeMM, eee eeeee, eee eeeee (MeMM8). Meeee eeeeeeeeeee ee eee eeeeeeee, eee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeeeeee eeeee/Me8M 88:88 ee 8:888), eeeeeeeee eeeeeeee eeeeeeee 88 (8.88e, 88%) eee eee eeeeeee 88; eeeee: 8.88e (88% eeeee eeeeeeeeeeeeeeeee ee eeeeeee); MM (MMMe8) νeee: 8888, 8888, 8888ee8; 8M MMM (MMMe8, δ): 8.8 (e, 8M), 8.8 (e, 8M), 8.8 (e, 8M).

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