The reaction of 3-cyclopropyl propargylic carboxylates with Au(I) and Au(III) catalysts affords selectively 5-(E)-alkylidenecyclopentenyl acetates via [3,3]-sigmatropic rearrangement the carboxylic moiety followed by cyclopropyl ring opening cyclization. DFT calculations have been performed, supporting a two-step no-intermediate mechanism along cyclization coordinate. stereoselective formation exocyclic alkenes is kinetically controlled in first these events. Although stereospecific nature...

Electronic and steric factors influence the enantioselectivity of formation pyrrolidines 1 in an asymmetric variant well-known Pd-catalyzed cycloiso-merization 1,6-enynes to give 1,4-dienes [Eq. (a)]. First hints importance these were obtained by varying R group enyne substituents on P-aryl groups chiral ligand bis[(diarylphosphanyl)ethyl]biferrocene (TRAP*). = Si(alkyl)3, alkyl.

Nonclassical chirality transfer? Depending on the substitution pattern of propargyl acetates, a gold-catalyzed homologous Rautenstrauch reaction generates either 5- or 6-membered ring systems (see scheme). The stabilization cationic intermediates is crucial for this to succeed. underlying principle good transfer observed could be gold-stabilized nonclassical carbocations having configurational stability.

In the presence of a Lewis acid, β,γ-unsaturated ketones and oximes or imines undergo nucleophilic addition to produce zwitterion intermediates, subsequent oxy-2-azonia-Cope rearrangements give homoallylic amides. case 2-vinylcycloalkanones, process results in ring enlargement, providing novel route 9- 16-membered lactams. The preparative significance this protocol was evidenced by short synthesis macrocyclic alkaloid motuporamine G. stereochemistry-defining step oxy-azonia-Cope...

Abstract Sulfur-containing compounds are some of the strongest odorants. The perception their odors often depends on concentration as well chemical, diastereo- and enantiomeric purity. Even if present only in trace amounts, they may change overall olfactory impressions fragrant mixtures, which makes art composing perfumes both difficult rewarding. In fruity area, such 8-mercapto-p-menthan-3-one (37), p-menthene-8-thiol (59), 3-mercapto-hexanol (62) Oxane® (100) have gained unimpeachable...

Conceptually different: This allyltransfer reaction is catalyzed by Lewis acids (LAs) and proceeds atom-economically disproportionation of the carbonyl groups through organized oxonia-Cope transition states (see scheme). A stereoselective [n+4] ring enlargement leads to a variety macrolides with 9- 16-membered rings. Detailed facts importance specialist readers are published as "Supporting Information". Such documents peer-reviewed, but not copy-edited or typeset. They made available...

Abstract Simple allenyl ethers have been shown to be efficiently activated by cationic gold(I) catalysts form reactive dienophiles in intermolecular Diels–Alder reactions. A range of different dienes give the cycloaddition products moderate excellent yields and good selectivity.

Musk made to odor: A new oxy-oxonia-Cope macrocyclization (3Z)-configured cycloalk-3-en-1-yl formates is reported, which useful in the synthesis of unsaturated and saturated macrocyclic ketones (see scheme). The synthesized structures provide insight into structure–odor correlation musks, making it likely for linear alicyclic musks address same olfactory receptors. Detailed facts importance specialist readers are published as "Supporting Information". Such documents peer-reviewed, but not...

Abstract A new Lewis acid‐catalyzed endo ‐selective Prins bicyclization of γ,δ‐unsaturated aldehydes or ketones with a broad range to dioxabicyclo[2.2.2]octanes is disclosed. When using chiral BINOL‐derived N ‐triflylphosphoramide (NTPA) as catalyst and glyoxylate esters substrates, the cross‐dimerization afford functionalized bicyclic acetals excellent diastereo‐ enantioselectivities.

Abstract This article describes the design and optimization of an effective organocatalytic three‐component domino α‐methylenation/Diels–Alder reaction to produce vinyl‐substituted cyclohexenecarboxaldehydes in a highly regioselective fashion. In these one‐pot transformations, 2‐formyl‐1,3‐butadienes ( 4 ) were prepared situ from α,β‐unsaturated aldehydes formalin subsequently trapped with variety buta‐1,3‐dienes. The outcomes reactions dependent on electronic properties dienes....

Elektronische und sterische Faktoren beeinflussen die Enantioselektivität der Bildung von Pyrrolidinen 1 durch eine asymmetrische Variante bekannten Pd‐katalysierten Cycloisomerisierung 1,6‐Eninen zu 1,4‐Dienen erheblich [Gl. (a)]. Durch Variation R im Enin Arylsubstituenten verwendeten chiralen Bis‐[(diarylphosphanyl)ethyl]biferrocen‐Liganden TRAP* wurden erste Hinweise auf Gewichtung dieser erhalten (R = Si(Alkyl) 3 , Alkyl). magnified image

Jasmine oil contains only 5% of the active constituent methyl epijasmonate (1a) in equilibrium with jasmonate (1b). Multigram quantities 1a can be synthesized a highly diastereoselective fashion from fumarate (S)-ethyl lactate and cyclopentadiene. The intermediates thereby obtained serve as building blocks for synthesis nearly all jasmonoids.

An unexpected gold(I)-catalyzed homo-Rautenstrauch rearrangement of 1-cyclopropyl propargylic esters to cyclohexenones is disclosed. This represents new evidence for the recently discussed gold-stabilized nonclassical carbocation character intermediates in gold catalysis. A mechanistic study proved partial chirality transfer from optically active propargyl acetates.

Nichtklassischer Chiralitätstransfer? Je nach Substitutionsmuster des Propargylacetats liefert eine goldkatalysierte homologe Rautenstrauch-Reaktion fünf- oder sechsgliedrige Ringsysteme (siehe Schema). Die Stabilisierung kationischer Intermediate ist für erfolgreiche Reaktion unabdingbar. Der Grund den beobachteten guten Chiralitätstransfer könnten goldstabilisierte nichtklassische Carbokationen mit konfigurativer Stabilität sein.

Abstract Recently, we reported a novel access to 2,2‐diethyl‐3‐[( E / Z )‐prop‐1‐en‐1‐yl]cyclobutanone by an intramolecular nucleophilic substitution with allylic rearrangement ( S N i ′) of )‐6‐chloro‐3,3‐diethylhept‐4‐en‐2‐one. The ring closure reaction was found proceed selective syn ‐displacement the leaving group. This method now applied total synthesis junionone, olfactorily interesting cyclobutane monoterpenoid isolated from Juniperus communis , L. ′ Ring ketone enolate...

Abstract Silicon compounds 1b – 3b are sila‐analogues of the galbanum odorants α‐galbanone ( 1a ), α‐spirogalbanone 2a and nor ‐α‐galbanone 3a respectively. Sila‐α‐galbanone sila‐α‐spirogalbanone 2b sila‐ ) were synthesized in multistep syntheses isomerically pure form, starting from Me 2 SiCl , (CH =CH) =CH)SiCl, Hydroformylation vinylsilanes, followed by either ring‐closing aldol condensation or alkene metathesis, key steps these syntheses. The C/Si pairs / studied for their olfactory...

Abstract A general method to synthesize functionalized allyl α‐amino acid derivatives through an irreversible oxy‐2‐azonia‐Cope rearrangement is reported. In the presence of AlCl 3 , reaction imino ethyl glyoxalates with various β,γ‐unsaturated ketones furnished corresponding derivatives. The key success this amide bond formation, which makes irreversible. This system constitutes a new strategy for synthesis unusual glycine derivatives, are valuable synthetic intermediates. An efficient and...

Abstract Dieser Aufsatz ist die Fortsetzung unseres Berichtes über neuesten Trends der Riechstoffchemie aus dem Jahr 2000 und fasst Entwicklungen letzten 20 Jahren zusammen. Dem selben Duftspektrum folgend, werden besonders richtungsweisende Captives (patentgeschützte Riechstoffe, nicht frei verkäuflich sind) vorgestellt, Einteilung in Geruchsfamilien “fruchtig”, “grün”, “marin”, “blumig”, “würzig”, “holzig”, “Ambra” “Moschus” wird auch dieser Übersicht beibehalten. Das Design von...

Konzeptionell anders: Diese Allylübertragung wird durch Lewis-Säuren (LA) katalysiert und verläuft über atomökonomische Disproportionierungen von Carbonylgruppen in organisierten Oxonia-Cope-Übergangszuständen (siehe Schema). Eine stereoselektive [n+4]-Ringerweiterung führt zu einer Vielzahl Macroliden mit 9- bis 16-gliedrigen Ringen.

Mechanistic studies on the intramolecular nucleophilic substitution with allylic rearrangement (SNi' reaction) and a new stereoselective access to substituted cyclobutanones are reported. 4,4-Dialkyl-5-oxohex-2E-en-1-yl methanesulfonates 4 were converted 2,2-dialkyl-3-vinylcyclobutanones 6 by SNi' ring closure. The stereochemical analysis of reaction was achieved through closure (6S)-6-chloro-3,3-diethylhept-4E-en-2-one (S)-17, defined absolute configuration C(6), leading...

A sequential Diels-Alder reaction/rearrangement sequence was developed for the synthesis of diverse functionalized bicyclo[2.2.1]heptanes as novel floral and woody odorants. The outcome rearrangement depended on substitution pattern dienes. 2D NMR analysis has established correct relative configuration bicyclo[2.2.1]heptanone, which originally misassigned. Furthermore, when initiating DA reaction catalyzed by a chiral Lewis acid, bicyclo[2.2.1]heptane derivatives including (+)-herbanone can...