Synthesis of a fluorine analog of hematoporphyrin by ring closure

Omote, Masaaki; Andõ, Akira; Takagi, Toshiyuki; Koyama, Mayumi; Kumadaki, Itsumaro

doi:10.1016/0040-4020(96)00858-7

Cited by 16 publications

(7 citation statements)

References 5 publications

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“…Cognizant that the degree of stereoselectivity depends upon the effectiveness of the chiral auxiliary in inducing asymmetric complexation, and thus the distance between the site of the auxiliary and the helical axis, we explored the value of incorporating a chiral centre directly adjacent to the dipyrrin: such a motif is rare for pyrroles [12][13][14][15][16][17] and extremely rare for dipyrrins. 16,18,19 β-Keto pyrroles are readily available through Knorr-type syntheses 20,21 and asymmetric reduction would generate a chiral alcohol. Further derivitization would serve to incorporate the pyrrole into a dipyrrin and thus place a chiral centre directly adjacent to the dipyrrinato unit ( Figure 2).…”

Section: Figure 1 Complexation Of Bis(dipyrrin)s With Varying Linkermentioning

confidence: 99%

“…The lability is caused by the electronrich nature of the pyrrole ring facilitating racemization at the pseudobenzylic position. Kumadaki provided a viable solution to potential racemization of this nature through the use of 4-(2,2,2trifluoro-1-hydroxyethyl)-substituted pyrroles 18,19 in the construction of homochiral haematoporphyrins. 16 We herein report our work with 4-(2,2,2-trifluoro-1-hydroxyethyl)substituted dipyrrins.…”

Section: Figure 1 Complexation Of Bis(dipyrrin)s With Varying Linkermentioning

confidence: 99%

“…Literature precedence supports the stereochemical stability of the (2,2,2-trifluoro-1hydroxyethyl) moiety under acidic conditions, 16,18,19 but we were concerned that the MacDonald- HPLC-analysis ( Figure S1) was used to determine that S-6, synthesized using S-3, had retained its enantiopurity during the MacDonald-type coupling step. Thus, with a source of enantiopure S-5 in hand, and having secured both the synthesis and the stereochemical stability of dipyrrins bearing the 4-(2,2,2-trifluoro-1-hydroxyethyl)-group, efforts progressed to investigating the stability of the corresponding complexes and assessing the affects of the electron-withdrawing substituent, essential for stability of the chiral centre, upon complexation.…”

Section: Scheme 1 Synthesis Ofmentioning

confidence: 99%

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Synthesis of dipyrrins bearing chirality adjacent to the conjugated skeleton — Electron-poor pyrroles exhibit dramatically reduced nucleophilicity

Beshara¹,

Pearce²,

Thompson³

2008

Can. J. Chem.

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With the aim of furthering our investigations into the asymmetric complexation of dipyrrinato ligands, a dipyrrin bearing a stereogenic centre directly adjacent to the conjugated skeleton was synthesized. The electron-withdrawing nature of the chiral 4-(2,2,2-trifluoro-1-hydroxyethyl)- substituent significantly reduced the nucleophilicity of corresponding pyrroles, such that 2,2′-symmetrically substituted bis(dipyrrin)s bearing this motif were inaccessible. Furthermore, solutions of mononuclear dipyrrinato complexes were found to be less stable to acid-catalyzed decomplexation than the corresponding dinuclear complexes.Key words: dipyrrin, dipyrromethene, complexation, electron-poor pyrrole, chirality.

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Section: Figure 1 Complexation Of Bis(dipyrrin)s With Varying Linkermentioning

confidence: 99%

Section: Figure 1 Complexation Of Bis(dipyrrin)s With Varying Linkermentioning

confidence: 99%

Section: Scheme 1 Synthesis Ofmentioning

confidence: 99%

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Synthesis of dipyrrins bearing chirality adjacent to the conjugated skeleton — Electron-poor pyrroles exhibit dramatically reduced nucleophilicity

Beshara¹,

Pearce²,

Thompson³

2008

Can. J. Chem.

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“…Many reactions for the synthesis (or functional group interconversion) of pyrroles were first introduced several decades ago, with little refinement having been reported since then. Benzyl 3,5-dimethyl-pyrrole-2-carboxylate 1 is a very useful precursor in the synthesis of functionalized pyrroles, dipyrromethenes and other multi-pyrrolic systems [1][2][3]. The -free position allows for further substitution of the pyrrole.…”

Section: Introductionmentioning

confidence: 99%

Microwave‐accelerated synthesis of benzyl 3,5‐dimethyl‐pyrrole‐2‐carboxylate

Regourd

Comeau

Beshara

et al. 2006

Journal of Heterocyclic Chem

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m ic ro wa ve en er gyEt hylen e g lyco l, p -TS A m ic ro wa ve en er gyBenzyl 3,5-dimethyl-pyrrole-2-carboxylate, a very useful pyrrole in porphyrin and dipyrromethene synthesis, can be synthesized via the Knorr-type reaction, but in low yield. Alternative routes to benzyl 3,5-dimethyl-pyrrole-2-carboxylate have been developed involving the trans-esterification of ethyl 3,5-dimethyl-pyrrole-2-carboxylate and the de-acetylation of benzyl 4-acetyl-3,5-dimethyl-2-carboxylate, both precursors being easily obtained using the Knorr reaction. These traditional methods involve treatment of the known products with a strong basic solution or heating for extended periods which often lead to decomposition. The use of microwave energy to promote these two reactions proves to be an extremely efficient way to obtain benzyl 3,5-dimethyl-pyrrole-2-carboxylate quickly, in high yield, and in excellent purity with no need for recrystallization. Of particular note is the use of catalytic sodium methoxide in benzyl alcohol, rather than stoichiometric amounts of sodium benzoxide, to effect benzylation.

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Section: Introductionmentioning

confidence: 99%

Microwave‐Accelerated Synthesis of Benzyl 3,5‐Dimethyl‐pyrrole‐2‐carboxylate.

et al. 2007

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Pyrrole derivatives R 0120Microwave-Accelerated Synthesis of Benzyl 3,5-Dimethyl-pyrrole-2-carboxylate.-Microwave irradiation is used to accelerate transesterification and deacetylation reaction, resp., to the title compound (III). The optimization of the reaction conditions is discussed. -(REGOURD, J.; COMEAU, I. M.; BESHARA, C. S.; THOMPSON*, A.; J. Heterocycl. Chem. 43 (2006) 6, 1709-1714; Dep. Chem., Dalhousie Univ., Halifax, Nova Scotia B3H 4J3, Can.; Eng.) -H. Haber

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Synthesis of a fluorine analog of hematoporphyrin by ring closure

Cited by 16 publications

References 5 publications

Synthesis of dipyrrins bearing chirality adjacent to the conjugated skeleton — Electron-poor pyrroles exhibit dramatically reduced nucleophilicity

Synthesis of dipyrrins bearing chirality adjacent to the conjugated skeleton — Electron-poor pyrroles exhibit dramatically reduced nucleophilicity

Microwave‐accelerated synthesis of benzyl 3,5‐dimethyl‐pyrrole‐2‐carboxylate

Microwave‐Accelerated Synthesis of Benzyl 3,5‐Dimethyl‐pyrrole‐2‐carboxylate.

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