Cyclopropyl Aldehydes Research Articles

Substitution-Dependent Ring-Opening Hydrosilylation or Dehydrogenative Hydrosilylation of Cyclopropyl Aldehydes and Ketones Catalyzed by Au Nanoparticles.

The reaction between hydrosilanes and aryl-substituted cyclopropyl aldehydes or ketones catalyzed by Au nanoparticles supported on TiO2 provides two distinct ring-opening reaction motifs depending on the substituents. 2-Aryl-substituted cyclopropyl carbonyl compounds form linear enol ethers via formal silyl hydride addition on the carbon atom bearing the aryl group. Under the reaction conditions, the hydrosilylation adducts undergo hydrolytic silyl deprotection to form acyclic aldehydes or ketones. For 2,2-arylalkyl- or 2,2-diaryl-substituted cyclopropyl carbonyl compounds, a ring-opening dehydrogenative hydrosilylation pathway is solely observed yielding chromatographically stable silyloxy-1,3-dienes. In the presence of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), the reaction is inhibited, indicative of a radical pathway. The proposed intermediate α-cyclopropyl silyloxy radicals undergo radical-clock ring-opening to form benzyl radicals, which may either be captured by the hydrosilane H atom (for 2-aryl-substituted substrates) to form linear silyl enol ethers or eliminate H2 and form silyloxy-1,3-dienes in the case of the bulkier 2,2-disubstituted ones.

Thiol-Mediated α-Amino Radical Formation via Visible-Light-Activated Ion-Pair Charge-Transfer Complexes.

Visible-light-activated electron donor-acceptor complexes offer distinct reaction pathways for the synthesis of complex molecules under mild conditions. Herein, we report a method for the reductive generation of α-amino radicals via the reaction of a visible-light-activated ion-pair charge-transfer complex formed between an in situ-generated alkyl-iminium ion and a thiophenolate. This distinct activation mode is demonstrated through the development of a multicomponent coupling reaction to form substituted aminomethyl-cyclopentanes from secondary amines, cyclopropyl aldehydes, and alkenes. The operationally straightforward transformation displays broad scope and provides a means to generate cyclic amine-containing scaffolds from readily available feedstocks.

Au Nanoparticle‐Catalyzed Silaboration of Aryl‐Substituted Cyclopropyl Aldehydes Forming Rearranged β‐Boronate Silyl Enol Ethers

2‐Aryl‐substituted cyclopropyl aldehydes undergo an unprecedented Au nanoparticle‐catalyzed silaboration leading to rearranged linear β‐boronate‐bearing silyl enol ethers. Formation of these products is attributed to the ring opening radical clock rearrangement of the intermediate α‐cyclopropyl radical into a benzyl radical.

Synthesis of 1-hydrocarbon substituted cyclopropyl silyl ketones

The synthesis of cyclopropyl silyl ketones possessing a hydrocarbon group at 1-position of three-membered ring was investigated. The reaction of sulfoxonium ylide with α,β-unsaturated acylsilanes derived from α,β-unsaturated aldehydes did not afford the desired acylsilane derivatives. Instead, the corresponding silyl enol ethers were yielded exclusively. On the other hand, the Corey-Chaykovsky cyclopropanation of α-substituted α,β-unsaturated aldehydes proceeded well to give 1-substituted cyclopropyl aldehydes. The silyl substitution of formyl proton in the obtained aldehydes via umpolung of carbonyl group afforded the target acylsilanes.

ChemInform Abstract: The Cyclopropylimine Rearrangement/Povarov Reaction Cascade for the Assembly of Pyrrolo[3,2‐c]quinoline Derivatives.

AbstractPyrrolo[3,2‐c]quinoline derivatives are prepared using anilines and cyclopropyl aldehyde as starting material.

The cyclopropylimine rearrangement/Povarov reaction cascade for the assembly of pyrrolo[3,2-c]quinoline derivatives

Simple combination makes complexity. An efficient assembly of pyrrolo[3,2-c]quinoline derivatives from anilines and cyclopropyl aldehyde is disclosed.

ChemInform Abstract: Total Syntheses of Solandelactones E and F

AbstractReview: 77 refs.

Probing the Mechanism of Cyanobacterial Aldehyde Decarbonylase Using a Cyclopropyl Aldehyde

Cyanobacterial aldehyde decarbonylase (cAD) is a non-heme diiron oxygenase that catalyzes the conversion of fatty aldehydes to alkanes and formate. The mechanism of this chemically unusual reaction is poorly understood. We have investigated the mechanism of C1-C2 bond cleavage by cAD using a fatty aldehyde that incorporates a cyclopropyl group, which can act as a radical clock. When reacted with cAD, the cyclopropyl aldehyde produces 1-octadecene as the rearranged product, providing evidence for a radical mechanism for C-C bond scission. In an alternate pathway, the cyclopropyl aldehyde acts as a mechanism-based irreversible inhibitor of cAD through covalent binding of the alkyl chain to the enzyme.

Stereoselective routes to aryl substituted γ-butyrolactones and their application towards the synthesis of highly oxidised furanocembranoids

Titanium chelate addition of aryl nucleophiles to cyclopropyl aldehyde 6 followed by a tin-catalyzed one-pot retro-aldol, acetalisation and lactonisation sequence afforded cis and trans γ-aryllactone acetals. A γ-furyllactone derived by this approach was further transformed in two steps to model compounds for the oxidised northeastern sectors of selected Pseudopterogorgia diterpenoids.

Organocatalytic asymmetric cyclopropanation of α,β-unsaturated aldehydes with arsonium ylides

A novel organocatalytic asymmetric cyclopropanation of α,β-unsaturated aldehydes with arsonium ylides using diphenylprolinol silylether as a catalyst is described. A variety of chiral cyclopropyl aldehydes are obtained in moderate to good yields with up to 99:1 dr (diastereomeric ratio) and 99% ee under simple and mild reaction conditions.

Gold(I)‐Catalyzed Oxidative Rearrangements.

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Gold(I)-Catalyzed Oxidative Rearrangements

A series of gold(I)-catalyzed oxidative rearrangement reactions of alkynes using sulfoxides as stoichiometric oxidants are reported. The reactions are postulated to proceed through intermolecular oxygen atom transfer from the sulfoxide to gold(I)−carbenoid intermediates. Under the conditions for gold(I)-catalyzed oxidative rearrangement, 1,6-enynes are isomerized to cyclopropyl aldehydes, homopropargyl azides produce pyrrolones, acetylenic α-diazoketones form cyclic en-1,4-diones, and propargylesters produce 2-acyloxyenals.

Highly enantioselective oxidation of cis-cyclopropylmethanols to corresponding aldehydes catalyzed by chloroperoxidase.

Chloroperoxidase (CPO) catalyzes the enantioselective oxidation of cyclopropylmethanols, such as 2-methylcyclopropylmethanol, to cyclopropyl aldehydes using tert-butyl hydroperoxide as the terminal oxidant. In all cases, CPO oxidation of cis-cyclopropanes shows much higher enantioselectivity than with the trans isomers, although CPO gives similar catalytic activity on both isomers. This presents the first example for a heme enzyme that catalyzes the enantioselective oxidation of cyclopropylmethanols. This finding enables a novel route to the synthesis of optically active cyclopropane derivatives, which occur widely in natural products and compounds of pharmaceutical interest. In addition, chiral cyclopropane molecules may be useful model substrates to investigate reaction mechanisms of CPO and the related cytochromes P450.

Novel preparation of cis,cis-trisubstituted cyclopropane nucleosides

Novel cyclopropane nucleosides, cis-2′, cis-3′-bis(hydroxymethyl)cyclopropyl thymine 4a and adenine 4b were synthesized. The stereoselective ring contraction of cyclobutyl bromohydrin 8 afforded cyclopropyl aldehyde 9 with a cis,cis configuration. After oxidation, conversion to amide and Hofmann's rearrangement, methyl carbamate 12 was obtained. Its basic hydrolysis yielded amine 13, then the target molecules were obtained by construction of bases.

Cycloaddition routes to tricyclo[5.4.01,7.02,9]undecanes: a direct total synthesis of (+)-longifolene via an intramolecular Diels-Alder strategy

The total synthesis of the sesquiterpene (+)-longifolene (1) by an intramolecular Diels-Alder cycloaddition strategy is described. Addition of methyllithium to the epoxyfulvene 13, derived from cyclopentadiene and 3,4-epoxy-2-butanone, led to an exo-tet cyclization of the resulting cyclopentadienyl anion to generate the spiro[2.4]hepta-4,6-diene alcohol 14. Resolution of this material was effected via its menthyl carbonate derivative 15. Oxidation of the (+)-R-alcohol with active MnO 2 afforded the cyclopropyl aldehyde 16 which was condensed with the anion derived from methyl 3-methylcrotonate in the presence of cadmium chloride to generate an unsaturated lactone or an unsaturated ester

Etude des petits cycles—XXVIII : Regression de cycle generale de cyclobutanols—I. Halohydrines-1,2, diols-1,2 et epoxydes correspondants

Methods for preparing 2-bromo and 2-tosyloxy cyclobutanols ( 1a and 1b) and 1,2-cyclobutanediols ( 6, 7, 8, 10 and 11), starting from 2-oxocyclobutanol 5 and 1,2-cyclobutanedione 9, have been studied. The cyclobutanols 1a and 1b undergo ring contraction in basic media while the 1,2-cyclobutanediols contract in acidic media or on heating. This ring contraction, reported previously for epoxycyclobutanes, affords cyclopropyl aldehydes or ketones in high yields.

Cyclopropylcarbinyl-oxo-carboniumions. A solvolytic basis for the cyclopropylcarbinyl-oxo-carbonium ion

Hydrolysis of 4,6-O-benzylidene-3-deoxy-3-C-(iodomethyl)-D-allal (1) in neutral buffered medium with or without silver ion assistance gives the cyclopropyl aldehyde 4 as the only product. Methanolysis of 1 gives an equal mixture of the α and β anomers of methyl 4,6-O-benzylidene-2,3-C-methylene-2,3-dideoxy-D-allopyranosides (6 and 7). These results indicate that the cyclopropylcarbinyl-oxo-carboniumion (2), is produced with unit efficiency in solvolyses in neutral media, and the formation of both diasteriomers (6 and 7) requires the complete absence of bicyclobutonium ion (9) resonance contribution to the stabilized intermediate, and implies a strong contribution from the oxo-carbonium ion 10. In basic media compound 1 undergoes quantitative dehydroiodination to the conjugated diene, 4,6-O-benzylidene-1,2,3-trideoxy-3-C-methylene-D-ribo-hex-1-enopyranose(8).