Multiconfigurational Dynamics Explain Photochemical Reactivity and Torquoselectivity Towards Fluorinated Polyacetylenes

The discovery of the conductivity of polyacetylene ignited the field of organic electronic materials. Functionalizing polyacetylenes with electron withdrawing groups (e.g., fluorine), has theoretically been shown to increase the air-stability of PAs and open new avenues in organic electronics. Burns and coworkers recently reported a novel synthetic route to fluorinated polyacetylenes which utilizes as a key step the completely stereoselective photochemical electrocyclic ring-closing of hexafluorinated dienes. This photochemical torquoselective (photo-torquoselective) reaction is, to our knowledge, the first of its kind. While the torquoselectivity model (Houk and co-workers) describes the stereospecificity of thermal electrocyclic reactions, no such reactivity model exists for their photochemical counterpart. We have used multiconfigurational quantum chemical calculations and ab initio molecular dynamics simulations to describe this reaction and to determine the origin of its stereoselectivity. We show that the reaction proceeds through the S1 excited state with a lifetime of 988 fs. This reaction lies along an energetically unfavorable pathway which results in a reaction quantum yield of approximately 0.9%. We predict that the reaction pathway to the unobserved product lies 0.2 eV (4.6 kcal mol−1) higher in energy than the pathway to the observed isomer. The unobserved isomer brings adjacent fluorine substituents to within 2.67 and 2.60 Å of each other at the S1/S0 crossing point, resulting in a closed-shell repulsion. This repulsion is responsible for increasing the energy of the unobserved pathway which directs the reaction exclusively to the observed product.

Multiconfigurational Dynamics Explain Photochemical Reactivity and Torquoselectivity Towards Fluorinated Polyacetylenes

The discovery of the conductivity of polyacetylene ignited the field of organic electronic materials. Functionalizing polyacetylenes with electron withdrawing groups (e.g., fluorine), has theoretically been shown to increase the air-stability of PAs and open new avenues in organic electronics. Burns and coworkers recently reported a novel synthetic route to fluorinated polyacetylenes which utilizes as a key step the completely stereoselective photochemical electrocyclic ring-closing of hexafluorinated dienes. This photochemical torquoselective (photo-torquoselective) reaction is, to our knowledge, the first of its kind. While the torquoselectivity model (Houk and co-workers) describes the stereospecificity of thermal electrocyclic reactions, no such reactivity model exists for their photochemical counterpart. We have used multiconfigurational quantum chemical calculations and ab initio molecular dynamics simulations to describe this reaction and to determine the origin of its stereoselectivity. We show that the reaction proceeds through the S1 excited state with a lifetime of 988 fs. This reaction lies along an energetically unfavorable pathway which results in a reaction quantum yield of approximately 0.9%. We predict that the reaction pathway to the unobserved product lies 0.2 eV (4.6 kcal mol−1) higher in energy than the pathway to the observed isomer. The unobserved isomer brings adjacent fluorine substituents to within 2.67 and 2.60 Å of each other at the S1/S0 crossing point, resulting in a closed-shell repulsion. This repulsion is responsible for increasing the energy of the unobserved pathway which directs the reaction exclusively to the observed product.

Multiconfigurational Dynamics Explain Photochemical Reactivity and Torquoselectivity Towards Fluorinated Polyacetylenes

The discovery of the conductivity of polyacetylene ignited the field of organic electronic materials. Functionalizing polyacetylenes with electron withdrawing groups (e.g., fluorine), has theoretically been shown to increase the air-stability of PAs and open new avenues in organic electronics. Burns and coworkers recently reported a novel synthetic route to fluorinated polyacetylenes which utilizes as a key step the completely stereoselective photochemical electrocyclic ring-closing of hexafluorinated dienes. This photochemical torquoselective (photo-torquoselective) reaction is, to our knowledge, the first of its kind. While the torquoselectivity model (Houk and co-workers) describes the stereospecificity of thermal electrocyclic reactions, no such reactivity model exists for their photochemical counterpart. We have used multiconfigurational quantum chemical calculations and ab initio molecular dynamics simulations to describe this reaction and to determine the origin of its stereoselectivity. We show that the reaction proceeds through the S1 excited state with a lifetime of 988 fs. This reaction lies along an energetically unfavorable pathway which results in a reaction quantum yield of approximately 0.9%. We predict that the reaction pathway to the unobserved product lies 0.2 eV (4.6 kcal mol−1) higher in energy than the pathway to the observed isomer. The unobserved isomer brings adjacent fluorine substituents to within 2.67 and 2.60 Å of each other at the S1/S0 crossing point, resulting in a closed-shell repulsion. This repulsion is responsible for increasing the energy of the unobserved pathway which directs the reaction exclusively to the observed product.

Indolylvinyl Ketones: Building Blocks for the Synthesis of Natural Products and Bioactive Compounds

Indolylvinyl ketones are valuable building blocks that can be utilized for the synthesis of numerous natural products and bioactive molecules containing an indole core motif. Herein, we describe their application for the total synthesis of some alkaloids, their analogues, and a variety of other important compounds, with an emphasis on biologically active examples.1 Introduction2 Functionalization of the Enone C=C Bond2.1 Reduction2.2 Michael Addition2.3 Cycloaddition3 Transformation of the Carbonyl Group3.1 Reduction3.2 Knoevenagel Reaction3.3 Addition of Organometallic Compounds3.4 Olefination4 Reactions Involving the Enone Conjugate System С=С–С=О4.1 Reactions with 1,2-Dinucleophiles4.2 Reactions with Compounds Bearing an Active Methylene Group4.3 Reactions with 1,3-Dinucleophiles4.4 Reactions with 1,4-Dinucleophiles5 Functionalization of the Enone Methylene Group C(O)–CH2R5.1 Acylation/Crotonic Condensation and Related Transformations5.2 Enolization6 Functionalization of the Indole Core6.1 [4+2] Cycloaddition6.2 [3+3] Annulation6.3 Electrocyclic Reactions7 Miscellaneous8 Conclusions

Dienamine-Induced Divinylcyclopropane-Cycloheptadiene Rearrangements

Sigmatropic rearrangements constitute an important group of pericyclic reactions. In contrast to cycloaddition reactions, examples of catalytic variants of electrocyclic reactions and sigmatropic rearrangements are still scarce in the chemical literature. Herein, we report the first organocatalytic Cope rearrangement of in situgenerated divinylcyclopropanes. The reactive motif is generated by condensation of 4-(2-vinylcyclopropyl)but-2-enal derivatives and a secondary amine catalyst to form a transient dienamine. The cycloheptadiene products can be obtained in high yield and excellent diastereoselectivity. Importantly, the reaction was demonstrated to be stereospecific, proceeds under mild conditions, and shows broad functional group tolerance. <br>