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Issue 7, 2011
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Facile synthesis of a B,D-tetradehydrocorrin and rearrangement to bacteriochlorins

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Abstract

Tetradehydrocorrins contain an A–D ring junction and a level of saturation intermediate between that of a corrin (characteristic of vitamin B12) and that of a corrole. Self-condensation of a p-tolyl-substituted dihydrodipyrrin-acetal (DHDPA-T) in CH2Cl2 containing Yb(OTf)3 at room temperature afforded the corresponding free base B,D-tetradehydrocorrin (TDC-T) as the sole macrocycle in 77% yield. The presence of a geminal dimethyl group in each of the reduced rings in TDC-T affords stability toward adventitious dehydrogenation. Treatment of TDC-T to acidic conditions results in rearrangement and loss of methanol to give a bacteriochlorin with or without a 5-methoxy substituent; the yield was 56% (5-methoxybacteriochlorin MeOBC-T), 35% (MeOBC-T) or 20% (5-unsubstituted bacteriochlorin HBC-T) with TMSOTf/CH2Cl2, BF3·OEt2/CH3CN or BF3·OEt2/CH2Cl2, respectively. TDC-T undergoes regioselective bromination with NBS to give the 10-bromotetradehydrocorrin in 22% yield. The conversion of the (non-aromatic) tetradehydrocorrin to the (aromatic) bacteriochlorin reflects the relative stability of the two macrocycles and indicates the former may be an intermediate—kinetically trapped or transient depending on catalysis conditions—upon dihydrodipyrrin-acetal self-condensation.

Graphical abstract: Facile synthesis of a B,D-tetradehydrocorrin and rearrangement to bacteriochlorins

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Publication details

The article was received on 14 Jan 2011, accepted on 28 Feb 2011 and first published on 11 Apr 2011


Article type: Paper
DOI: 10.1039/C1NJ20027E
Citation: New J. Chem., 2011,35, 1376-1384
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    Facile synthesis of a B,D-tetradehydrocorrin and rearrangement to bacteriochlorins

    K. Aravindu, M. Krayer, H. Kim and J. S. Lindsey, New J. Chem., 2011, 35, 1376
    DOI: 10.1039/C1NJ20027E

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