877305-39-0Relevant academic research and scientific papers
Geometric synthesis of porphyrin rods
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Page/Page column 18-22; 25, (2010/11/27)
A method of making a compound of Formula I′ comprises reacting a compound of the formula DLCHO, with a compound of the formula to produce the compound of Formula I′. Methods of using the compounds are also described, particularly as intermediates for the synthesis of porphyrin rods, which porphyrin rods are in turn useful for (among other things) the production of molecular memory devices.
Alkylthio unit as an α-pyrrole protecting group for use in dipyrromethane synthesis
Thamyongkit, Patchanita,Bhise, Anil D.,Taniguchi, Masahiko,Lindsey, Jonathan S.
, p. 903 - 910 (2007/10/03)
The synthesis of porphyrin precursors requires the successive introduction of substituents at the pyrrole α- and α′-positions (2- and 5-, respectively). An α-pyrrole substituent that serves as a temporary masking agent and is not deactivating would greatly facilitate such syntheses, particularly for β-(3,4)-unsubstituted pyrroles, but has heretofore not been available. A series of α-RS groups (R = Me, Et, n-decyl, Ph) have been investigated in this regard, including the determination of the kinetics of substitution at the pyrrolic 3-, 4-, and 5-positions and the application to dipyrromethane formation. The RS group was readily introduced into the pyrrole α-position by the reaction of 2-thiocyanatopyrrole (prepared from pyrrole, ammonium thiocyanate, and iodine) and the corresponding Grignard reagent RMgBr. Each 2-alkylthio group activated the pyrrole ring toward deuteration at the 3- or 5- (vs 4-) position. The dipyrromethane synthesis was carried out using a 2:1 ratio of 2-(RS)pyrrole/benzaldehyde with a catalytic amount of InCl3 at room temperature in the absence of any solvent. The α-RS group was removed by hydrodesulfurization using Raney nickel or nickel complexes. This stoichiometric synthesis using the α-RS-protected pyrrole is in contrast to the traditional synthesis that employs an aldehyde and 25-100 mol equiv of pyrrole. Six meso-substituted dipyrromethanes were prepared by the reaction of 2-(n-decylthio)pyrrole/aldehyde/InCl3 (2.2:1:0.2 ratio) followed by hydrodesulfurization. Other reactions of the 1,9-bis(RS)dipyrromethane include oxidation to give (i) the 1,9-bis(RS)dipyrrin or (ii) the 1,9-bis(RSO 2)dipyrromethane, which underwent subsequent complexation with dibutyltin dichloride. In summary, under mild reaction conditions, the 2-alkylthio group is readily introduced to the pyrrole nucleus, directs electrophilic substitution to the 5-position, and is readily removed as required for elaboration of porphyrinic precursors.
