Search

Herein, we report a one-pot Lewis acid mediated synthesis of bi- and triarylpropanal derivatives and their corresponding isomeric ketones from aromatic enol ethers. This transformation takes place via nucleophilic attack of enol ethers to electron-rich benzyl alcohols. The substrate scope of this indicates that it might proceed via quinomethoxy methide as a key intermediate leading to propanal derivatives, and their Wagner–Meerwein rearrangement afforded isomeric ketones. Further, this methodology was applied for the synthesis of (±)-tetrahydronyasol, propterol A, and 1,3-diarylpropane.

An expeditious synthetic methodology leading to substituted metahalophenols and their corresponding methyl ether derivatives through acidmediated fragmentation of suitably substituted dihalonorbornyl ketones has been devised. The reaction sequence consists of TBTHmediated TBTH is trinbutyltin hydride selective bridgehead halogen reduction of easily accessible Diels–Alder adducts derived from 1,2,3,4tetrahalo5,5dimethoxycyclopentadiene and βsubstituted vinyl acetates, with subsequent conversion into the requisite bicyclic ketones by a twostep hydrolysisoxidation approach. An extensive mechanistic investigation based on isotope labeling and cross experiments has been carried out and plausible mechanistic pathways based on these results have been proposed. The absence of halogen atoms at the bridgehead positions steers the reaction through a novel pathway involving the incorporation of proton or deuterium followed by elimination of HX or DX, so the described methodology also provides a reliable route to orthoparadideuteratedphenolic derivatives.

The supported rutheniumcatalyzed oxidation of the 1,2dihaloalkene moiety in tetrahalonorbornyl derivatives possessing acid labile functionalities to afford the corresponding αdiketones is demonstrated. The protocol was successfully applied in the synthesis of a cyclopentaannulated δlactone derived from Dmannitol.

A series of γ-oxo esters 27–34 was prepared from methyl 2-silyloxycyclopropanecarboxylates 1–9 as key building blocks in a flexible modular synthesis. Their samarium diiodide promoted cyclization to benzannulated cyclooctanol derivatives was systematically investigated. Samarium ketyl compounds derived from aldehydes 27 and 28 mainly provided tricyclic γ-lactones 38 and 39 as a result of a cis-selective ring-closure process, whilst the related ketones 29–31 underwent trans-selective reductive cyclization to furnish the expected benzannulated cyclooctanol derivatives 43–45 in moderate to excellent yields. With cyclohexanones 33 and 34 an interesting stereochemical matched/mismatched situation was observed. Whereas diastereomers 33a and 34a smoothly afforded tricyclic products 47 and 48 in good yields, compound 33b with apparently mismatched configuration did not undergo the samarium diiodide promoted ring-closure process. An explanation for this intriguing behaviour is presented, together with an explanation for the cis/trans selectivity. Tricyclic γ-lactone 38 could be smoothly deprotonated at one bridgehead and the generated lithium enolate was trapped with suitable alkyl halides. Remarkably, a clean α-hydroxylation of 38 and 39 by direct employment of molecular oxygen was possible, providing high yields of the corresponding tertiary alcohols 54 and 55. These results demonstrate that the cyclization products prepared can easily be converted into higher functionalized benzannulated cyclooctane derivatives.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

A simple and convenient three-step protocol for the synthesis of pentasubstituted tribromophenols based on the acid-catalyzed Grob-type fragmentation of the bicyclic ketone precursors 8a–e in high overall yield is described. The bicyclic ketones 8a–e were obtained in two steps starting from the Diels–Alder cycloadducts 5a–e of β-substituted vinyl acetates and tetrabromo-5,5-dimethoxycyclopentadiene. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

We report a highly regio- and diastereoselective allylindium addition to norbornyl α-diketones that leads to acyloins. The diastereoselection in the case of monosubstituted derivatives greatly depends on the nature of the 5-endo substituents. Non-chelating groups direct the addition from the sterically less congested exo-face, diagonal to the substituent, while chelating substituents, such as an alkoxy or acetoxy units, induce a complete reversal in the selectivities. The presence of an oxygen atom directly linked to the norbornyl framework is crucial for eliciting a chelating effect because an acetoxymethyl (−CH2OAc) group exhibits normal behavior and acts as a non-chelating group. The dramatic influence (reversal) of an apparently innocuous exo-Me substituent is noted. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

A novel, efficient, and regio‐ as well as diastereoselective conversion of non‐enolizable bicyclic α‐diketones into synthetically useful acyloins mediated by indium metal is described. The reduction is highly diastereoselective, leading exclusively to endo‐acyloins (endo‐hydroxyl groups) in excellent yields, and tolerates a variety of sensitive substituents, such as acetate, ester, and bridgehead halogens. The regioselectivity in the reductions of monosubstituted α‐diketones varied from 70:30 to 100:0 for the two possible isomeric alcohols. The methodology is extended to the synthesis of highly functionalized cyclopentane carboxaldehydes, potential building blocks in organic syntheses, by cleavage of the acyloins by treating them with Pb(OAc)4in MeOH/PhH. Allylindium additions to carboxaldehydes 22have been found to be highly diastereoselective.

A novel, efficient, and regio- as well as diastereoselective conversion of non-enolizable bicyclic α-diketones into synthetically useful acyloins mediated by indium metal is described. The reduction is highly diastereoselective, leading exclusively to endo-acyloins (endo-hydroxyl groups) in excellent yields, and tolerates a variety of sensitive substituents, such as acetate, ester, and bridgehead halogens. The regioselectivity in the reductions of monosubstituted α-diketones varied from 70:30 to 100:0 for the two possible isomeric alcohols. The methodology is extended to the synthesis of highly functionalized cyclopentane carboxaldehydes, potential building blocks in organic syntheses, by cleavage of the acyloins by treating them with Pb(OAc)4 in MeOH/PhH. Allylindium additions to carboxaldehydes 22 have been found to be highly diastereoselective.

Donor−acceptor substituted cyclopropane derivatives 4a−g were synthesized in good yields from ketones, via the corresponding silyl enol ethers 2a−g, by cyclopropanation with methyl diazoacetate followed by alkylation using o-iodobenzyl iodide. The γ-oxo esters 5a−g were prepared in high yield, employing NEt3 · 3 HF. A novel Pd-catalyzed one-pot transformation of 4a−f into 1,2-disubstituted indanes 6a−f was accomplished using either CsF (Method A or B) or Bu4NF (Method C) as the fluoride source to achieve the in situ ring-opening of 4a−f. The two reagents CsF and Bu4NF function in a complementary manner. For example, CsF works better with enones 4b and 4c, while Bu4NF functions well with aryl/alkyl ketones 4d−f. Pd-catalyzed Heck cyclization of vinyl ketone 5a furnished mainly the 7-exo-trig cyclization product 7 but isopropenyl ketone 5b gave a moderate yield of indane derivative 6b, arising from enolate arylation. When the carbonyl group in 5b was protected, a novel tricyclic compound 13 was obtained in low yield.

Radical mediated selective carboncarbon bond forming processes and hydrodehalogenation at the bridgehead positions of tetrahalonorbornenes (which are readily accessible, inexpensive and precursors for numerous applications) is described.

Short synthetic routes to the title compounds 1,-3, from readily available Diels-Alder adduct 5 of 6,6-dimethylfulvene and acrylonitrile are described.

Norbornyl α‐diketones undergo facile Grob fragmentation to afford α‐ketoenols such as (II).

The title compounds are prepared by acid‐catalyzed fragmentation of dihalonorbornyl ketones (IV).

Oxidation of phenols with PbO2in combination with HClO4affords the target compounds whose electrochemical properties are studied in detail.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform 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.

ChemInform 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.

ChemInform 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.

ChemInform 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.

ChemInform 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.

For Abstract see ChemInform Abstract in Full Text.

For Abstract see ChemInform Abstract in Full Text.

For Abstract see ChemInform Abstract in Full Text.

For Abstract see ChemInform Abstract in Full Text.

For Abstract see ChemInform Abstract in Full Text.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.