Janovsky reactions between cyclopentadienyliron complexes of substituted benzenes and carbanions derived from ketones

Abstract

RONALD G. SUTHERLAND, RATAN L. CHOWDHURY, ADAM ~' I~R K o , and CHOI CHUCK LEE. Can. J. Chem. 64,203 1 (1986). Janovsky reactions were carried out between various r16-substituted benzene-qs-cyclopentadienyliron cations containing at least one electron-withdrawing substituent in the complexed arene and the enolate-carbanion derived from acetone, butanone, or 3-pentanone. Highly colored adducts were obtained from reactions of the cyclopentadienyliron (CpFe) complexes of nitrobenzene, cyanobenzene, p-tolylsulfonylbenzene, benzoylbenzene, o-, p-, or m-nitrotoluene, and o-, p-, or m-dichiorobenzene with acetone in aqueous KOH, the products being derived from e.xo-addition of the acetonyl anion regioselectively at a position ortho to an electron-withdrawing substituent. For example, reaction of the q6-nitrobenzene-$-cyclopentadienyliron cation (la) with acetone in aqueous KOH gave (~,S)-(1-5-~~-1-nitro-6-exo-(2-oxo-l-~ro~~l)-c~clohexadien~l)(~~-c~clo-pentadieny1)iron (2a), isolated as a purple solid. Similarly, reaction of the nitrobenzene complex l a with 3-pentanone in aqueous KOH gave two diastereomeric adducts, (R,R-S,S)-and (R,S-S,R)-(1-5-~~-l-nitro-6-exo-(3-oxo-2-~ent~l)-cyclohexadienyl)(r15-cyclopentadienyl)iron ( l l a , b). Reactions of the CpFe complexes of chlorobenzene and o-or pdichlorobenzene with butanone in aqueous KOH were also investigated. In each case, three Janovsky adducts, two being diastereomers, were obtained from addition of the two carbanions derived from loss of either a-proton of butanone. Potential synthetic applications via these Janovsky adducts are pointed out since their treatment with ammonium ceric nitrate could lead to demetallation-oxidation; for example, (2,5-dichlorophenyl)propanone, a new compound, was obtained from the adduct formed between the p-dichlorobenzene complex and the acetonyl anion. Chem. 64,2031Chem. 64, (1986 On a effectue la reaction de Janovsky entre divers cations benzene q6-substitues ~~c l o~e n t a d i~n~l -~~ de fer contenant au moins un substituant Clectro-attracteur dans le complexe a r h e et les carbanions Cnoliques derives de I'acCtone, de la butanone ou de la pentanone-3. On obtient des adduits fortement lors des rkactions des complexes cyclopentadiCnyles de fer (CpFe) et du nitrobenzene, du cyanobenzkne, du p-tolylsulfonylbenzene. du benzoylbenzi.ne des o-, p-ou m-nitrotolukne et des o-, p-ou m-dichlorobenzene avec l'acetone dans du KOH aqueux. Les produits proviennent d'une addition exo rCgiosClective de I'anion acCtonyle en position ortho d'un substituant Clectro-attracteur. Par exemple, la reaction du cation nitro-q6 benzenecyclopentadiCnyle-q5 de fer (la) avec I'acCtone dans du KOH aqueux donne du (nitro-1 (0x0-2 propyl-1)-exo-6 cyclohexadienyl--r15-1 ,5) (cyclopentadiCnyl--r15) de fer (R,S) (2a) qui a Ct C is016 sous la forme d'un solide de couleur pourpre. Le complexe l a du nitrobenzene reagit de la mCme f a~o n avec la pentanone-3 dans du KOH aqueux pour donner deux adduits diastCreoisomeres soit les nitro-l (0x0-3 pentyl-2)-exo-6 (cyclohexa...

Addition of Metal Enolate Derivatives to Unactivated Carbon−Carbon Multiple Bonds

“…441 More than 20 years ago, Sutherland and co-workers reported the addition of the acetonyl anion by reaction of complexes 281 of arenes bearing electronwithdrawing substituents with acetone in the presence of aqueous KOH. [442][443][444] Interestingly, high ortho selectivity (with respect to the electron-withdrawing group) was observed even in the case of highly hindered 2,6-dimethyl substituted compounds (Scheme 312). In a related approach, the acetonyl anion was also reported to react with heterocyclic complexes 282.…”

“…Stabilized carbanions that have been added onto (η 6 -arene)Fe + Cp complexes include ketone enolates and nitrile stabilized anions . More than 20 years ago, Sutherland and co-workers reported the addition of the acetonyl anion by reaction of complexes 281 of arenes bearing electron-withdrawing substituents with acetone in the presence of aqueous KOH. − Interestingly, high ortho selectivity (with respect to the electron-withdrawing group) was observed even in the case of highly hindered 2,6-dimethyl substituted compounds (Scheme ). In a related approach, the acetonyl anion was also reported to react with heterocyclic complexes 282 . , Selective addition was observed for the metal complexed ring; addition was again ortho to the carbonyl group.…”

Synthesis of Aromatic Nitriles via the Temporary Complexation of Nitroarenes to the Cationic Cyclopentadienyliron Moiety

“…It has been established that the complexation of an arene to a variety of transition-metal moieties, including those of iron, manganese, and chromium, facilitates nucleophilic aromatic substitution as well as nucleophilic addition to the ring. − Our earlier work illustrates this behavior via the introduction of the cyano group to cyclopentadienyliron complexes of aromatic ethers . Recently, we were successful in the synthesis of a large number of substituted (aniline)cyclopentadienyliron complexes .…”

“…Studies have shown that nucleophilic addition of hydride or carbon nucleophiles to a complexed arene usually occurs exo to the arene ring. ,, Substituent effects play a key role as to where the addition will occur. The presence of a strong electron-withdrawing group allows for addition ortho to the functional group …”