Carbene Adducts Research Articles

„Dimerisierungsprodukte”︁ von 1,2‐Cyclooctadien?

“Dimerization Products” of 1,2‐Cyclooctadiene?The conversion of 8,8‐dibromobicyclo[5.1.0]octane (2) with methyllithium is known to yield kinetically labile 1,2‐cyclooctadiene (1). This strained cyclic allene readily dimerizes at ambient temperature. The 1‐methyl derivative enjoys greater kinetic stability, but nevertheless only three [2 + 2]‐cycloaddition products can be isolated after workup. Whereas the dimerization products 17, 22, 23, 24 can be predicted from recent studies, the carbene adducts 15 and 16 were not yet reported. The stereochemistry of 17 and 22 is determined by X‐ray structure analysis of their Diels‐;Alder adducts with tetracyanoethylene.

Reaction of dichlorocarbene with substituted 3,4-dihydroisoquinolines and 1-methylene-1,2,3,4-tetrahydroisoquinolines

Reaction of dichlorocarbene with 3,3-dialkyl-3,4-dihydroisoquinolines results in the formation of gemdichloroazirino[2,1-a]isoquinolines, which are in turn converted to 3-benzazepinones upon hydrolysis. Reaction of dichlorocarbene with the ethyl ester or amide of (3,3-dimethyl-1,2,3,4-tetrahydroisoquinolin-1-ylidene)acetic acid is accompanied by rearrangement of the intermediate carbene adducts at the enamine C=C bond and results in the formation of a 1-azadiene, 3-(3,3-dimethyl-3,4-dihydroisoquinolin-1-yl)-3-chloroacrylic acid ethyl ester, and a spirolactam, 3,3-dimethyl-3-chlorospiro[1,2,3,4-tetrahydroisoquinoline-1,2′-pyrrole]-5′(2′H)-one, respectively.

From Dichlorocyclopropanes to Furans and Cyclopentadienes via Vinylcarbenes

AbstractBase‐induced elimination of dichlorocarbene adducts 2 to 9‐alkoxyphen threnes 1 leads to furans 6, presumably via cyclopropenes 3 which undergo rearrangement to vinylcarbenes 4 and CH insertion. By the same sequence, the 9‐substituted alkylphenanthrene adduct 10 and 14 afford cyclopentadienes 11 and 15. Carbene adducts of simple enol ethers, however, react differently and give preferentially 2‐chloroalken‐2‐ones.

Synthesis of 1-benzoxepines from dichlorocarbene adducts of chromenes

Synthesis of 1-benzoxepines by dehydrochlorination of carbene adducts of chromenes has been carried out. Different alkyl-, alkylidene-, alkoxy-, aryl- and hetarylsubstituted 1-benzoxepines were obtained.

Steuerung einer reaktionsverzweigung durch geeignete phasentransfer-katalysatoren anwendungen der phasentransfer-katalyse 37.

The influence of phase transfer catalyst structure on a branching of reaction paths is recorded. An almost complete change-over of mechanisms can be achieved. Reaction of allyl bromide with bromoform/sodium hydroxide/catalyst yields carbene adduct 1 and displacement products 2 and 3 . Two new and unusual catalysts, AsPh 4Cl and [Ph 3PNPPh 3] Cl, give substitution: addition ~10:1, wheras NMe4Cl and benzo-15-crown-5 lead to ~1:4, both at high conversions.

Fluoroacrylic acid esters

Two synthetic routes to α-fluoroacrylates are described: Chlorofluorocarbene is generated from CHFCl 2 under phase- transfer catalysed conditions. In situ addition of this carbene to an enol ether gives a cyclopropane. Then this compound is transformed into α-fluoroacrolein. Photochemical bromination of this aldehyde gives an acid bromide. This intermediate can lead to various α-fluoroacrylic acid esters, particularly to the phenyl ester, which is of interest for aeronautic. The enol ether can be replaced by 1-ethoxy-l-phenoxy ethylene. Thermolysis of the carbene adduct leads directly to phenyl α-fluoroacrylate.

Anwendungen der phasentransfer-katalyse: XXXII. Trimethylsilyl-trichloracetat: Ein neues ausgangsmaterial fur dichlorcarben

Reflux of trimethylsilyl trichloroacetate and an alkene with the addition of a phase transfer catalyst (4 mol.%) and solid, dry potassium fluoride in an inert nonpolar solvent (toluene, chloroform, or dichloromethane) leads to dichloro- carbene adducts. This is a non-basic mild method, which can easily be carried out.

Addition of an electrophilic carbene to an electron-deficient olefin. Kinetics of benzylchlorocarbene-diethyl fumarate reaction

Benzylchlorocarbene reacts as an electrophile with electronic deficient diethyl fumerate; the dependence of product ratio on [DEF] is consistent with formation of a carbene adduct.

ChemInform Abstract: STUDIES IN THE TRICYCLOOCTANE SERIES. V. DEHYDROHALOGENATION OF THE BIS(DIHALOCARBENE) ADDUCTS OF SOME METHOXYCYCLOHEXADIENES

AbstractDie durch Birch‐Reduktion der entsprechenden aromatischen Substrate erhaltenen Cyclohexadiene‐(1,4) (I) liefern bei der Dihalogencarbenaddition die Tricyclooctanderivate (II), deren Dehydrohalogenierung untersucht wird.

Studies in the tricyclooctane series. V. Dehydrohalogenation of the Bis-dihalocarbene adducts of some methoxycyclohexadienes

The bis-dichloro and bis-dibromo carbene adducts (1c-h) of 1-methoxy-, 1,4-dimethoxy- and 1,5-dimethoxy-cyclohexa-1,4-diene undergo regiospecific dehydrohalogenation by strong base to the 4,8,8- trihalomethoxybicyclo[5,1,0]octa-2,4-dienes (7c-h), in contrast to the 1,7-dimethoxytricyclooctane(1i) and its methyl derivatives (1j-m), which are unchanged. The dienes (7c-h) are resistant to further dehydrohalogenation.

ChemInform Abstract: CARBENES IN THE SYNTHESIS OF HETEROCYCLES (REVIEW)

The syntheses of heterocyclic compounds by reactions of carbenes with carbon-heteroatom multiple bonds, isomerization of unstable adducts of carbenes to carbon-carbon bonds, and the incorporation of carbenes in C-H, C-N, and C-O bonds are examined.

Carbenes in the synthesis of heterocycles (review)

The syntheses of heterocyclic compounds by reactions of carbenes with carbon-heteroatom multiple bonds, isomerization of unstable adducts of carbenes to carbon-carbon bonds, and the incorporation of carbenes in C-H, C-N, and C-O bonds are examined.