Double Claisen Rearrangement Research Articles

Construction of Unusual Amino Acid derivatives and Bis‐Fused Oxacycles via Ring‐Closing Metathesis

AbstractBenzofurans and benzoxepines are key structural elements present in several natural products and medicinally important targets. Here, we describe an easy‐to‐execute strategy for the synthesis of benzofurans and benzoxepines, by employing Claisen rearrangement and ring‐closing metathesis (RCM) as key steps. Amino acid L‐tyrosine and 1,8‐dihydroxy‐anthraquinone were converted into modified oxacycles in good yields. The RCM approach has been used to produce bis‐fused benzofuran, bis‐fused benzoxepine, and unusual α‐amino acid (AAA) derivatives containing heterocyclic units. Unusual AAA derivatives are among the most important source for new peptide drugs and these AAA derivatives containing oxacycles are useful in designing many natural and unnatural products. Bis‐fused benzofuran and bis‐fused benzoxepine derivatives were also synthesized by the application of double Claisen rearrangement and two‐directional RCM as key steps starting with 1,8‐dihydroxy anthraquinone.

Synthetic Approach to the ABCD Ring System of Anticancer Agent Fredericamycin A via Claisen Rearrangement and Ring-Closing Metathesis as Key Steps.

A new synthetic strategy to the ABCD ring system of the anticancer agent fredericamycin A (NSC-305263) was realized by the Diels–Alder reaction and olefin metathesis as key steps. The tactics developed here for the construction of the ABCD ring system also involve double Claisen rearrangement followed by a retro-Diels–Alder reaction and ring-closing metathesis. The metathesis approach performs a key role in the construction of A and D rings of the ABCD core unit. More importantly, ABCD fragment synthesis was accomplished without the involvement of protecting groups.

Unified total synthesis of amorfrutins A and C via the Claisen rearrangement.

A concise, unified total synthesis of the two prenylated aromatic polyketides amorfrutins A and C, which exhibit various medicinally important biological profiles such as antimicrobial, PPARγ modulating and quorum sensing inhibitory activities, has been achieved from commercially available 3,5-dimethoxybenzaldehyde in 38% and 10% overall yields through nine and ten steps, respectively. The key transformation for the synthesis of amorfrutin A was the Claisen rearrangement of a mono-O-(1,1-dimethylallyl)resorcinol derivative to install the C3-prenyl substituent, while that for the synthesis of amorfrutin C was the double Claisen rearrangement of a di-O-(1,1-dimethylallyl)resorcinol derivative to introduce the two prenyl groups at the C3 and C5 positions all at once.

ChemInform Abstract: A New Synthetic Strategy to 2,3‐Diallyl‐1,4‐quinones via One‐Pot Double Claisen Rearrangement and Retro Diels—Alder Reaction.

AbstractA simple alternative method to 2,3‐diallyl‐1,4‐quinone derivatives via a one‐pot double claisen rearrangement and retro Diels—Alder reaction sequence involving readily available starting materials is reported.

A new synthetic strategy to 2,3-diallyl-1,4-quinones via one-pot double Claisen rearrangement and retro Diels–Alder reaction

A simple and an efficient synthetic strategy to 2,3-diallyl-1,4-quinone derivatives via a highly reliable and 100% atom economic reactions such as Diels–Alder (DA) reaction, Claisen rearrangement (CR), and retro Diels–Alder (rDA) reaction as key steps is reported.

Asymmetric Syntheses of the Flavonoid Diels-Alder Natural Products Sanggenons C and O.

Metal-catalyzed, double Claisen rearrangement of a bis-allyloxyflavone has been utilized to enable a concise synthesis of the hydrobenzofuro[3,2-b]chromenone core structure of the natural products sanggenon A and sanggenol F. In addition, catalytic, enantioselective [4+2] cycloadditions of 2'-hydroxychalcones have been accomplished using B(OPh)3/BINOL complexes. Asymmetric syntheses of the flavonoid Diels-Alder natural products sanggenons C and O have been achieved employing a stereodivergent reaction of a racemic mixture (stereodivergent RRM) involving [4+2] cycloaddition.

ChemInform Abstract: Diversity‐Oriented Approach to Cyclophanes via Claisen Rearrangement and Ring‐Closing Metathesis as Key Steps

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Design of new synthetic strategies to cyclophanes via ring-closing metathesis

A simple synthetic methodology to cyclophanes containing hydroxyl groups has been reported. The key steps involved here are: Grignard reaction, double Claisen rearrangement, and ring-closing metathesis. The strategy reported here is protecting group-free synthesis.

Diversity-oriented approach to cyclophanes via Claisen rearrangement and ring-closing metathesis as key steps

Among numerous reactions to prepare cyclophane derivatives, Claisen rearrangement reaction is very useful. We have prepared cyclophanes containing ethylene oxy bridge by double Claisen rearrangement reaction and ring-closing metathesis reaction as key steps.

Two-Directional Synthesis of 2,6-Dimethylpyrrolo[2,3-f]indole-4,8-dione by Double Claisen Rearrangement and Nitrene Cyclization

Two-Directional Synthesis of 2,6-Dimethylpyrrolo[2,3-f]indole-4,8-dione by Double Claisen Rearrangement and Nitrene Cyclization

Total Synthesis of Dihydrocodeine and Hydrocodone via a Double Claisen Rearrangement and C-10/C-11 Closure Strategy

Dihydrocodeine and hydrocodone were synthesized from bromobenzene in 16 and 17 transformations, respectively. The key steps involved the toluene dioxygenase-mediated dihydroxy­lation of bromobenzene by whole-cell fermentation with <i>E. coli</i> JM109(pDTG601A), Kazmaier–Claisen rearrangement of glycinate ester, Claisen rearrangement to set the C-13 quaternary center, and C-10–C-11 closure. Experimental procedures are provided for the key steps.

Polyphosphoric Acid Promoted Synthesis of 10,11-Dihydrobenzo[j]fluoranthen-12-one

A straightforward synthesis of 3,8-dimethoxy-10,11-dihydrobenzo[j]fluoranthen-12-ones 1 is reported in a seven-step route from biphenyl-4,4'-diol 2 via the transformation of a double Claisen rearrangement, cross metathesis with ethyl acrylate, and polyphosphoric acid (PPA)-promoted Friedel-Crafts electrophilic benzannulation in good yields.

Synthesis of novel H-shaped chromophores

A series of H-shaped chromophores with two parallel and non-conjugated D-π-A units have been synthesized, in which a 9,10-dihydroanthracene was employed as molecular backbone. The synthesis of these H-shaped chromophores 9a–11a was accomplished via an eight-step reaction, including double Claisen rearrangement, hydroboration–oxidation, Rieche formylation reaction, Knoevenagel condensation and Corey–Fuchs reaction, with a total yield about 12.5%. The corresponding mono-D-π-A unit compounds 9b–11b were also prepared in a similar procedure for the purpose of comparison. Crystal structures of three intermediates 5a, 7a and 8a were measured, which demonstrate that the two D-π-A units in a single H-shaped chromophore molecule are nearly arranged at the same direction. The studies of UV–vis spectra and the solvatochromic method indicate that the molecular second-order polarizabilities values (μβ) of H-shaped chromophores are remarkably increased compared with the corresponding mono-D-π-A unit reference compounds, without causing a large shift of the absorption band to longer wavelength.

Toward Generic Models of Hemoproteins

The versatility of a resorcinol-substituted phenanthroline-strapped porphyrin was enhanced by appending allyl chains via a double Claisen rearrangement. Two pyridine arms were then appended to the resorcinol oxygens. This multifunctional porphyrin is a suitable generic building block for the preparation of liposoluble heme protein models. X-ray characterization of the pentacoordinated zinc complex and the binding of a sixth imidazole ligand to the ferric complex both suggest a facilitated access to an empty distal site.

Synthesis of 2,5-Dihydrofuran-Fused Quinones from Ether-Tethered Diiododiyne

Biologically interesting 2,5-dihydrofuran-fused quinones were synthesized via the ruthenium-catalyzed [2 + 2 + 2] cycloaddition of an ether-tethered diiododiyne with alkynes, copper-catalyzed Ullmann coupling of the resultant fused p-diiodobenzenes with methanol or allyl alcohol, and subsequent oxidation of phenol derivatives. The double Claisen rearrangement of the bis(allyl) ether product furnished a diallylhydroquinone derivative, which underwent iron-catalyzed oxidation, ring-closing metathesis, and dehydrogenation to deliver 1,3-dihydronaphtho[2,3-c]furan-4,9-dione.

Synthesis of the Reported Structure of the Bisbenzoquinone Lanciaquinone, Isolated from Maesa lanceolata

Lanciaquinone, isolated from Maesa lanceolata, was originally assigned as a bisbenzoquinone with a C14-chain linking the two quinone rings. A synthesis of the reported structure, in which the key step is a double Claisen rearrangement, suggests that the structure of the natural product needs to be revised.

Formation of Arenes via Diallylarenes: Strategic Utilization of Suzuki–Miyaura Cross‐Coupling, Claisen Rearrangement and Ring‐Closing Metathesis

AbstractTwo new synthetic strategies for benzoannulation are reported. The first strategy is based on the Suzuki–Miyaura cross‐coupling reaction. To this end, various ortho‐diallylbenzene derivatives were prepared from the corrresponding diiodo derivatives by an allylation strategy using an allylboronate as coupling partner. These diallyl derivatives were subjected to a ring‐closing metathesis (RCM) and one‐pot dichlorodicyanoquinone (DDQ) oxidation sequence to deliver 2‐substituted naphthalenes. In the second strategy, a double Claisen rearrangement and RCM protocol have been used as key steps to give highly functionalized benzoannulated quinone derivatives.

Sequential Double Claisen Rearrangement and Two‐Directional Ring‐Closing Metathesis as a Route to Various Benzofused Bisoxepin and Bisoxocin Derivatives.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Sequential Double Claisen Rearrangement and Two-Directional Ring-Closing Metathesis as a Route to Various Benzofused Bisoxepin and Bisoxocin Derivatives

A synthetic strategy based on tandem application of double Claisen rearrangement and two-directional ring-closing metathesis reaction as key-steps has been developed for the synthesis of various hitherto unknown tri-, tetra- and pentacyclic benzofused bisoxepin and bisoxocin derivatives.

A New Protocol for Benzoannulation by Double Claisen Rearrangement and Ring‐Closing Metathesis Reactions as Key Steps.

AbstractFor Abstract see ChemInform Abstract in Full Text.