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Titolo:
A CONVENIENT SYNTHESIS OF 2-ALKYL-5,10,15,20-TETRAPHENYLPORPHYRINS - REACTION OF METALLO-2-NITRO-5,10,15,20-TETRAPHENYLPORPHYRINS WITH GRIGNARD AND ORGANOLITHIUM REAGENTS
Autore:
CROSSLEY MJ; HARDING MM; TANSEY CW;
Indirizzi:
UNIV SYDNEY,SCH CHEM SYDNEY NSW 2006 AUSTRALIA
Titolo Testata:
Journal of organic chemistry
fascicolo: 16, volume: 59, anno: 1994,
pagine: 4433 - 4437
SICI:
0022-3263(1994)59:16<4433:ACSO2->2.0.ZU;2-H
Fonte:
ISI
Lingua:
ENG
Soggetto:
2-SUBSTITUTED 5,10,15,20-TETRAPHENYLPORPHYRINS; PORPHYRINS; ION; METALLOPORPHYRINS; DEUTERIATION; TAUTOMERISM;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
28
Recensione:
Indirizzi per estratti:
Citazione:
M.J. Crossley et al., "A CONVENIENT SYNTHESIS OF 2-ALKYL-5,10,15,20-TETRAPHENYLPORPHYRINS - REACTION OF METALLO-2-NITRO-5,10,15,20-TETRAPHENYLPORPHYRINS WITH GRIGNARD AND ORGANOLITHIUM REAGENTS", Journal of organic chemistry, 59(16), 1994, pp. 4433-4437

Abstract

A new synthesis of 2-alkylporphyrins is reported. Treatment of metallo-2-nitro-5,10,15,20-tetraphenylporphyrins (M = Cu, Ni, Zn) 2-4 with alkylmagnesium halides affords the corresponding metallo-2-alkyl-5,10,15,20-tetraphenylporphyrins (alkyl = Me, i-Pr, Bu) 6-12 in moderate to good yield. The reaction proceeds by initial nucleophilic attack of the Grignard reagent at the beta-pyrrolic carbon next to that bearing the nitro group. The intermediate is protonated in workup to generate metallo-2-alkyl-3-nitro-2,3-dihydro-5,10, 15,20-tetraphenylporphyrin 5, which eliminates nitrous acid to give the corresponding 2-alkylporphyrin. The results of deuterium labeling experiments support this mechanism. The use of tert-butylmagnesium bromide and phenylmagnesium bromideas reagents does not lead to the corresponding 2-tert-butyl- or 2-phenylporphyrins but rather gives products from reductive processes. The reaction of tro-5,10,15,20-tetraphenylporphyrinato)-copper(II) (2) with tert-butylmagnesium bromide results in reductive denitration to givethe parent porphyrin 13, presumably due to elimination of isobutyleneand nitrous acid from an intermediate 2-tert-butyl-3-nitro-2,3-dihydroporphyrin. Reaction of 2 with phenylmagnesium bromide leads to a complicated mixture of products, the major one being the 2-(phenylamino) derivative 14 which results from reductive arylation of the nitro group. Preliminary studies show that butyllithium also reacts with 2, but the reaction is difficult to control and a complex mixture of over-reacted products results; in this case, 2-butylporphyrin 10 is at best isolated in 10% yield which compares unfavorably with the 56% yield of 10from the reaction involving the corresponding Grignard reagent.

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Documento generato il 24/09/20 alle ore 21:25:08