The reactivity of oxygen nucleophiles with aryl radicals in the SRN1 mechanism
作者:María T. Baumgartner、Adriana B. Pierini、Robert A. Rossi
DOI:10.1016/s0040-4039(00)74201-8
日期:1992.4
The photostimulated reaction of 2-naphthoxide ions 1 with o-dihalobenzenes in liquid ammonia gives the halosubstituted product 4 and the cyclized substituted product 5. This is the first report about the coupling of an aromatic σ radical with an oxygen functionality in the chain propagation cycle of the SRN1mechanism.
The first dynamic kinetic asymmetric transformation of racemic biaryl substrates on the basis of axial-to-central chirality transfer has been realized. Chiral Pd-NHC complexes were found to catalyze the dynamic kinetic asymmetric spiroannulation of 4-(2-bromoaryl)-naphthalen-1-ols (or 2'-bromo-[1,1'-biphenyl]-4-ols) with internal alkynes, affording a series of enantioenriched spirocyclic products bearing an all-carbon quaternary stereocenter in good yields (up to 95%) with excellent enantioselectivities (up to 97% ee).
Photostimulated reactions of o-dihalobenzenes with nucleophiles derived from the 2-naphthyl system. Competition between electron transfer, fragmentation, and ring closure reactions
作者:Maria T. Baumgartner、Adriana B. Pierini、Roberto A. Rossi
DOI:10.1021/jo00061a040
日期:1993.4
The photostimulated reaction of o-dihalobenzenes 2 with 2 naphthoxide ions 1-O gave the substitution product on carbon 1 of the naphthyl moiety with retention of halogen (1, Br, and Cl) 3 as well as the ring closure product benzo[b]naphtho[1,2-d]furan (4), with product 3 being an intermediate in the formation of 4. The products obtained in the photostimulated reaction of 2-naphthalenethiolate ions 1-S with 2 depend on the halogens. When both nucleofugal groups are iodine, only the ring closure product benzo[b]naphtho[1,2-d]thiophene (10) is obtained. With o-bromoiodobenzene, the photostimulated reaction gave 10 and the substitution product on sulfur with retention of bromine, while with o-chloroiodobenzene the only observed product was the substitution product on sulfur with retention of chlorine. The photostimulated reaction of 2 with 2-naphthaleneselenolate ions 1-Se gave the same amount of cyclized product benzo[b]naphtho[1,2-d]selenophene (14) and the substitution product on selenium without retention of halogen 15, although in an overall low yield. It is suggested that all these reactions occur by the S(RN)1 mechanism. Theoretical studies support the different behavior found with the nucleophiles derived from the 2-naphthyl system.