Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Siloxacyclopentenes as dienophile-linked directing groups in intramolecular Diels-Alder reactions.

ABSTRACT: The synthesis and intramolecular Diels-Alder reactions of trienes 5 and 6 with a siloxacyclopentene-constrained dienophile are described. These reactions provide the primary cycloadducts 7 and 8 with high diastereoselectivity. These cycloadducts possess trans-relationships between the ring fusion proton and the adjacent C(1) alkoxy group and can be further elaborated to alcohols 9 and 11 (via protiodesilylation) or to 10 and 12 (via Fleming-Tamao oxidation) depending on the substitutent R.

SUBMITTER: Halvorsen GT

PROVIDER: S-EPMC2650085 | biostudies-literature | 2008 Nov

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Siloxacyclopentenes as dienophile-linked directing groups in intramolecular Diels-Alder reactions.

Halvorsen Geoff T GT Roush William R WR

Organic letters 20081028 22

The synthesis and intramolecular Diels-Alder reactions of trienes 5 and 6 with a siloxacyclopentene-constrained dienophile are described. These reactions provide the primary cycloadducts 7 and 8 with high diastereoselectivity. These cycloadducts possess trans-relationships between the ring fusion proton and the adjacent C(1) alkoxy group and can be further elaborated to alcohols 9 and 11 (via protiodesilylation) or to 10 and 12 (via Fleming-Tamao oxidation) depending on the substitutent R. ...[more]

PMID: 18954061

Similar Datasets

Intramolecular Diels-Alder reactions of cyclopropenone ketals.

Project description:The first intramolecular cycloaddition reactions of cyclopropenone ketals with tethered electron-deficient, electron-rich, and neutral 1-substituted dienes are reported, constituting inverse electron demand, normal, and neutral Diels-Alder reactions, that provide exclusively the exo [4 + 2] cycloaddition products without the intervention of [1 + 2], [3 + 2], or [3 + 4] cycloadducts in reactions whose courses do not depend on the reaction conditions, the diene activating substituent, or the nature of the tethering.

| S-EPMC2912946 | biostudies-literature

Intramolecular Diels-Alder reactions of siloxacyclopentene constrained trienes.

Project description:The synthesis of siloxacyclopentene-constrained trienes 7 and 10 and studies of their IMDA cycloadditions are described. The use of appropriately chosen thermal or Lewis acid conditions allows for cycloadducts 3-6 to be obtained with high levels of diastereoselectivity. These adducts possess trans-relationships between the hydroxyl group and the adjacent ring fusion proton, a stereochemical relationship not previously attainable in IMDA reactions.

| S-EPMC2504012 | biostudies-literature

Cyclobutenone as a highly reactive dienophile: expanding upon Diels-Alder paradigms.

Project description:Cyclobutenone was employed as a dienophile in Diels-Alder cycloadditions, provide diverse and complex cycloadducts in good yields. Experimental outcomes indicated cyclobutenone to be more reactive than either cyclopentenone or cyclohexenone. In addition, cycloadducts bearing a strained cyclobutanone moiety were able to undergo regioselective ring expansions to produce corresponding cyclopentanones, lactones, and lactams, which are otherwise difficultly obtained by direct Diels-Alder reactions.

| S-EPMC2956739 | biostudies-literature

Intramolecular Diels-Alder reactions of cycloalkenones: translation of high endo selectivity to trans junctions.

Project description:Intramolecular Diels-Alder reactions of cyclobutenone and larger cycloalkenones are described. High levels of endo addition attained from Lewis acid catalysis translate to trans hydrindene junctions upon fragmentation of the tricyclic adducts.

| S-EPMC3464979 | biostudies-literature

Intramolecular Diels-Alder reactions of cycloalkenones: stereoselectivity, Lewis acid acceleration, and halogen substituent effects.

Project description:The intramolecular Diels-Alder reactions of cycloalkenones and terminal dienes occur with high endo stereoselectivity, both thermally and under Lewis-acidic conditions. Through computations, we show that steric repulsion and tether conformation govern the selectivity of the reaction, and incorporation of either BF3 or α-halogenation increases the rate of cycloaddition. With a longer tether, isomerization from a terminal diene to the more stable internal diene results in a more facile cycloaddition.

| S-EPMC3965351 | biostudies-literature

How Ionization Catalyzes Diels-Alder Reactions.

Project description:The catalytic effect of ionization on the Diels-Alder reaction between 1,3-butadiene and acrylaldehyde has been studied using relativistic density functional theory (DFT). Removal of an electron from the dienophile, acrylaldehyde, significantly accelerates the Diels-Alder reaction and shifts the reaction mechanism from concerted asynchronous for the neutral Diels-Alder reaction to stepwise for the radical-cation Diels-Alder reaction. Our detailed activation strain and Kohn-Sham molecular orbital analyses reveal how ionization of the dienophile enhances the Diels-Alder reactivity via two mechanisms: (i) by amplifying the asymmetry in the dienophile's occupied π-orbitals to such an extent that the reaction goes from concerted asynchronous to stepwise and thus with substantially less steric (Pauli) repulsion per reaction step; (ii) by enhancing the stabilizing orbital interactions that result from the ability of the singly occupied molecular orbital of the radical-cation dienophile to engage in an additional three-electron bonding interaction with the highest occupied molecular orbital of the diene.

| S-EPMC9400981 | biostudies-literature

Mechanism of the Intramolecular Hexadehydro-Diels-Alder Reaction.

Project description:Theoretical analysis of the mechanism of the intramolecular hexadehydro-Diels-Alder (HDDA) reaction, validated against prior and newly measured kinetic data for a number of different tethered yne-diynes, indicates that the reaction proceeds in a highly asynchronous fashion. The rate-determining step is bond formation at the alkyne termini nearest the tether, which involves a transition-state structure exhibiting substantial diradical character. Whether the reaction then continues to close the remaining bond in a concerted fashion or in a stepwise fashion (i.e., with an intervening intermediate) depends on the substituents at the remaining terminal alkyne positions. Computational modeling of the HDDA reaction is complicated by the significant diradical character that arises along the reaction coordinate, which leads to instabilities in both restricted singlet Kohn-Sham density functional theory (DFT) and coupled cluster theory based on a Hartree-Fock reference wave function. A consistent picture emerges, however, from comparison of broken-symmetry DFT calculations and second-order perturbation theory based on complete-active-space self-consistent-field (CASPT2) calculations.

| S-EPMC4729778 | biostudies-literature

Intramolecular [4 + 2] cycloadditions of iminoacetonitriles: a new class of azadienophiles for hetero Diels-Alder reactions.

Project description:Iminoacetonitriles participate as reactive dienophiles in stereoselective intramolecular hetero Diels-Alder reactions which afford substituted quinolizidines. The cycloadduct with exo-oriented cyano group is obtained as the major or exclusive product of the reaction as a consequence of the alpha-amino nitrile anomeric effect The alpha-amino nitrile moieties incorporated in the cycloadducts constitute latent iminium ions, which upon exposure to mild protic or Lewis acids are unmasked, setting the stage for further useful synthetic transformations. For example, reductive decyanation with NaBH3CN excises the cyano group, while Bruylants reaction with Grignard reagents and acetylides lead to alpha-substituted amines. The substrates for these [4 + 2] cycloadditions are prepared from readily available alcohols via a Mitsunobu coupling reaction with the previously unknown, easily prepared reagent HN(Tf)CH2CN followed by cesium carbonate promoted elimination of trifluoromethanesulfinate.

| S-EPMC2892977 | biostudies-literature

Rapid Access to Hydroxyfluoranthenes via a Domino Suzuki-Miyaura/Intramolecular Diels-Alder/Ring-Opening Reactions Sequence.

Project description:In this work, we developed an efficient method for the rapid construction of fluoranthene skeleton to access a variety of substituted hydroxyfluoranthenes. The 1-iodo-8-alkynylnaphthalene derivatives, which serve as substrates for the key fluoranthene-forming step, were prepared via selective monoalkynylative Sonogashira reactions of 1,8-diiodonaphthalene. The domino reaction sequence which involves a sequential Suzuki-Miyaura coupling, an intramolecular Diels-Alder reaction, and an aromatization-driven ring-opening isomerization has been shown to give substituted hydroxyfluoranthenes in up to 92% yield. This work demonstrates the utility of designing new domino reactions for rapid access to substituted polycyclic aromatic hydrocarbons (PAHs).

| S-EPMC9087347 | biostudies-literature

Dual Activation of Aromatic Diels-Alder Reactions.

Project description:The unusually fast Diels-Alder reactions of [5]cyclophanes were analyzed by DFT at the BLYP-D3(BJ)/TZ2P level of theory. The computations were guided by an integrated activation-strain and Kohn-Sham molecular orbital analysis. It is revealed why both [5]metacyclophane and [5]paracyclophane exhibit a significant rate enhancement compared to their planar benzene analogue. The activation strain analyses revealed that the enhanced reactivity originates from 1)?predistortion of the aromatic core resulting in a reduced activation strain of the aromatic diene, and/or 2)?enhanced interaction with the dienophile through a distortion-controlled lowering of the HOMO-LUMO gap within the diene. Both of these physical mechanisms and thus the rate of Diels-Alder cycloaddition can be tuned through different modes of geometrical distortion (meta versus para bridging) and by heteroatom substitution in the aromatic ring. Judicious choice of the bridge and heteroatom in the aromatic core enables effective tuning of the aromatic Diels-Alder reactivity to achieve activation barriers as low as 2?kcal?mol-1 , which is an impressive 35?kcal?mol-1 lower than that of benzene.

| S-EPMC6771859 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data