Preparation of Some Pyrrole-3,4-dicarboxylic Acid Derivatives and the Crystal Structure of 2-Methylpyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione

Arnold, D. P.; Nitschinsk, LJ; Kennard, Chl; Smith, Gregory L.

doi:10.1071/ch9910323

Cited by 9 publications

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“…Our first samples of the desired diazene precursors 17a of N -substituted-3,4-dimethylenepyrroles were obtained by rather impractical routes described elsewhere. 11a,17b Currently we prefer the synthetic approach shown in Scheme 1. It is based upon the ready availability of 3,4-dicarboethoxypyrrole 10 from the p- tosylmethyl isocyanide−fumaric ester addition − and incorporates as a crucial modification the use of the N-tosyl group in the intermediate 13 to suppress the heterolytic reactivity of the chloromethyl groups. Specific methods (Schemes 1 and ) for the conversion of 10 via 13 to the key intermediate N -tosylpyrrolodihydropyridazine biscarbamate 14f and for the replacement of the tosyl group of 14f by other N-substituents permit its application to a variety of derivatives.…”

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Tuning the Singlet−Triplet Energy Gap in a Non-Kekulé Series by Designed Structural Variation. The Singlet States of N-Substituted-3,4-dimethylenepyrrole Biradicals

et al. 1997

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Semiempirical quantum chemical calculations (AM1/CI and PM3/CI) confirm the qualitative perturbational prediction that electron-withdrawing groups on the ring nitrogen of a 3,4-dimethylenepyrrole should diminish the energy separation of the singlet and triplet states to near zero. Syntheses of a series of precursors of such biradicals have been developed. Study of the chemistry and spectroscopy of the biradicals has revealed persistent singlet states for the cases where the substituent is methyl, isobutyryl, and pivaloyl. In the cases of N-arenesulfonyl-3,4dimethylenepyrroles, both a singlet and a triplet form can be observed as persistent species. In this paper, the properties of the singlets in this series are described. Although energy transfer from the excited triplet state of the sensitizer xanthone to the diazene precursor of N-p-toluenesulfonyl-3,4-dimethylenepyrrole is observed by nanosecond timeresolved spectroscopy, the chemical behavior of the biradical intermediate is the same as that observed in the direct photolysis or thermolysis of the diazene. The reactive form of the biradical under these conditions appears to be the singlet. Experimental Design. Tuning the Multiplet Gap in N-Substituted-3,4-dimethylenepyrrole Biradicals.Prediction of the spacings of the lowest energy multiplets of π-conjugated non-Kekulé molecules is a stringent test of theory. Although in most cases these separations are difficult to measure, the effect of structure on the qualitative trends of their direction and magnitude should be estimable by theoretical calculation. We are particularly attracted to the use of computationally designed systematic structural variations as means of tuning the spacings and hence providing experimental tests of such estimates. The necessary elements of this approach are a parent system with near-degenerate multiplet states, a variable structural feature that can be used to perturb their separation, and a theoretical means for selecting potentially fruitful structural alterations. Since the singlet-triplet gap in such species can be made quite small, the tuning process ultimately might offer the power of choice over the multiplicity of the ground state.The disjoint hydrocarbon biradical tetramethyleneethane (TME, 1) provides a useful starting structure for such a process. Although the size of the energy separation between the lowest triplet and singlet states of TME is not yet known from experiment, theory 2 predicts a very small gap (E T -E S ∼ -1 to +2 kcal/mol). A heteroatom bridge connecting two termini of the TME molecule, as in previous work 3 from this laboratory on 3,4-dimethylenefuran and 3,4-dimethylenethiophene, introduces a variable source of electronic perturbation.The present paper describes the preparation and characterization of the singlet states of several such biradicals, and an accompanying paper 11b reports results of the search for the corresponding triplet states.Our present computational approach was implicit in theoretical considerations by Du, Hrovat, and Borden, 4 whic...

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Tuning the Singlet−Triplet Energy Gap in a Non-Kekulé Series by Designed Structural Variation. The Singlet States of N-Substituted-3,4-dimethylenepyrrole Biradicals

et al. 1997

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“…Arnold and co-workers have described the preparation of 2-substituted pyrrolo[3.4- c ]pyrrole-1,3-(2 H ,5 H )-diones (intermediate 5 ) for the 2-methyl and 2-benzyl derivatives. The method utilizes the 1,3-dipolar addition of the anion of tosylmethyl isocyanide (TMIC) to diethyl fumarate to form 3,4-diethylpyrroledicarboxylate.…”

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Poly(2-alkylpyrrolo[3.4-c]-1,3-(2H,5H)- dioxopyrrole-4,6-diyl)s. A Novel Class of Intramolecularly Hydrogen-Bonded, Conjugated Polymers

Pollack¹,

Kgobane²

1997

Macromolecules

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Polypyrrole has long been studied for its unique electronic and optical properties. 2 It is an inherently conducting polymer (ICP) due to both its conjugated π-system and its ready ability to be doped. Numerous studies have focused on its conductivity and nonlinear optical properties. The polymer is typically prepared via two routes. Pyrrole and 3-substituted or 3,4-disubstituted derivatives can be oxidized, either by electrochemical means or through the use of inorganic oxidants such as ferric chloride, to form an insoluble material with high conductivity. 3,4 Alternatively, various 2,5-disubstituted pyrroles can be polymerized through transition metal mediated coupling reactions. 5,6 This latter route typically produces linear oligomers that, depending on other substitution of the pyrrole ring, can have high conductivities and unique optical properties.Most of the unique electrooptical properties mentioned above derive from the extended π-system present in these polyheteroaromatics. Like most rigid-rod polymers, polypyrrole once formed is not readily processable. Several groups have attempted to add functionality at the 1, 3, and/or 4 position of the pyrrole ring to enhance the solubility of the resulting polymer. 3-6 However, the steric effects of these groups tend to decrease the coplanarity of the polymer backbone, thus compromising its electronic and optical properties. Recently, Tour 7 described a novel polypyrrole based on N-alkyl-3-oxopyrrolinium 4-oxides, in which there is the potential of strong favorable Coulombic interactions to stabilize the ring system's coplanarity. This is reflected in UV absorptions extending into the near-infrared. This polymer also exhibits unique solvatochromic behavior. We reasoned that a similar inter-ring interaction, based on self-complementary hydrogen-bonding, might also serve to enhance coplanarity as well as provide for the potential for interesting thermo-and solvatochromic behavior. This work reports on our initial investigation of these new materials.Our approach has been to design a pyrrole monomer capable of hydrogen-bonding through the NH proton to the adjacent monomer units in order to maintain planarity. This suggested a symmetric 3,4-disubstituted system. Using the N-H hydrogen as the hydrogen-bond donor, a 3,4-dicarbonyl system should generate a hydrogen-bonded ladderlike polymer.For a simple dimer, with X ) NCH 3 , a study of the relative energies of conformers calculated at the AM1 level of semiempirical theory 8 predicted that the minimum energy conformation is antiplanar (as shown above). The syn-planar conformer is predicted to be 15 kcal mol -1 higher in energy due to strong steric interactions between carbonyl groups on adjacent monomer units. There is no other conformational minimum predicted. For a trimer, the steric interactions of the two carbonyls on alternate rings and the hydrogen of the central monomer unit causes the system to go out of planarity. The most stable trimer (which we denote as an "r" triad) has a C 2 symmetry, with the C 2 axis g...

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Synthetic Uses of Tosylmethyl Isocyanide (TosMIC)

Leusen

2001

Organic Reactions

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TosMIC is the acronym for 4‐tolylsulfonylmethyl isocyanide or tosylmethyl isocyanide. It is the best‐known member of a series of about 25 sulfonyl‐substituted methyl isocyanides RSO 2 CH 2 NC collected in Chart 1 (p. 426). TosMIC is a multipurpose synthetic reagent. It is by far the most versatile synthon derived from methyl isocyanide. This chapter provides a complete account of the synthetic uses of TosMIC based on a literature search closed in January 1996, and supplemented with further data available to the authors. Also included are applications of some of the more important TosMIC homologs (TosCHRNC). TosMIC is the only commercially available sulfonylmethyl isocyanide. It is a stable, colorless, practically odorless solid, which can be stored at room temperature without decomposition. Four brief review papers on the chemistry of TosMIC have appeared, in 1980, 1987, 1993, and 1995. Several reviews on the chemistry of isocyanides in general are available. An effort has been made to make this chapter as complete as possible, in coverage both by tables and by references, with respect to the immediate objective: a survey of the “Synthetic Uses of TosMIC.” Emphasis is on the primary products derived from reactions of TosMIC and related isocyanides, with limited reference to the further utilization of these products. Thus, the next section gives a complete account of reductive cyanation, the conversion of aldehydes or ketones into cyanides with the use of TosMIC, but for obvious reasons synthetic applications of the product cyanides are not treated in this chapter. One of the subsequent sections describes the application of TosMIC to the synthesis of pyrroles, including 2,3‐divinylpyrroles, which are important precursors in a new synthesis of indoles. This latter transformation, made possible by the easy availability of the precursors through TosMIC chemistry, is afforded brief coverage. As a rule, reference to preliminary papers has been omitted when the same information is available from the corresponding full papers. The patent literature is covered highly selectively and is cited only when providing new and relevant information. Negative results of reactions are reported in the text or tables only when at least some relevant information is available with respect to the conditions of such unsuccessful attempts.

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Preparation of Some Pyrrole-3,4-dicarboxylic Acid Derivatives and the Crystal Structure of 2-Methylpyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione

Cited by 9 publications

References 0 publications

Tuning the Singlet−Triplet Energy Gap in a Non-Kekulé Series by Designed Structural Variation. The Singlet States of N-Substituted-3,4-dimethylenepyrrole Biradicals

Tuning the Singlet−Triplet Energy Gap in a Non-Kekulé Series by Designed Structural Variation. The Singlet States of N-Substituted-3,4-dimethylenepyrrole Biradicals

Poly(2-alkylpyrrolo[3.4-c]-1,3-(2H,5H)- dioxopyrrole-4,6-diyl)s. A Novel Class of Intramolecularly Hydrogen-Bonded, Conjugated Polymers

Synthetic Uses of Tosylmethyl Isocyanide (TosMIC)

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