Dichlorocarbene Adducts Research Articles

The Synthesis of 3-Phosphabicyclo[3.1.0]- hexane 3-Oxides and 1,2-Dihydrophosphinine 1-Oxides with Lipophilic P-Alkoxy Substituents by Ring Enlargement

A series of 1-alkoxy-3-phospholene 1-oxides available from the microwave-assisted direct esterification of 1-hydroxy-3-phospholene oxide was converted to the two diastereomers of 6,6-dichloro-3-phosphabicyclo[3.1.0]hexane 3-oxides by the addition of dichlorocarbene to the double bond. Thermolysis of the 3-phospholene oxide–dichlorocarbene adducts afforded the corresponding 1,2-dihydrophosphinine 1-oxides as a ca. 3:1 mixture of two double bond isomers. Relative stability of the isomers of the intermediates and the products and their stereostructures were evaluated by B3LYP/6-31G(d,p) calculations.

ChemInform Abstract: Base‐Promoted Reaction of Dichlorocarbene Adducts or Cyclic Enamines: A New Route to Annulated Pyrroles.

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 of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Base-Promoted Reactions of Dichlorocarbene Adducts of Cyclic Enamines: A New Route to Annulated Pyrroles

Treatment of the gem-dihalogenocyclopropanes 1-5 with potassium tert-butoxide or LDA results in the formation of the corresponding and annulated pyrroles 13-17, respectively.

Dichlorocarbene Adducts of Alkyl Enol Ethers as Precursors to Furans: Application to a Total Synthesis of the Furanosesquiterpene (.+‐.)‐Pallescensin A.

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.

Dichlorocarbene adducts of alkyl enol ethers as precursors to furans: application to a total synthesis of the furanosesquiterpene (±)-pallescensin A

A novel method for annulating furans to ketones, involving treatment of the dichlorocarbene adduct of the derived methyl enol ether with base, has been exploited in the synthesis of the title natural product 1 from the known trans-decalone 2.

Side-wall opening of single-walled carbon nanotubes (SWCNTs) by chemical modification: a critical theoretical study.

Single-walled carbon nanotubes (SWCNTs) have unique electronic, mechanical, and structural characteristics; consequently, promising applications derived from these materials, such as chemical sensors or nanometer-scale electronic devices, can be expected. Structurally altered nanotubes with appropriate addends should facilitate their use by improving solubility, processability, and ease of dispersion, as well as by providing sites for chemical attachment to surfaces and polymer matrices. Avexing problem is ascertaining the detailed structures of nanotube derivatives after their preparation. The characterization of functionalized SWCNTs is difficult; all experimental attempts to determine the precise location and mode of addition of newly attached groups have failed. SWCNT adducts with possible three-membered rings (3MRs) that result from oxygen, methylene, and NH additions are simple but very important side-wall functionalized derivatives. Oxidation reactions are used widely to purify nanotubes, and the electrical properties of carbon nanotubes are extremely sensitive to oxygen exposure. Methylene and NH adducts are the prototypes of the recently synthesized covalently bonded dichlorocarbene and nitrene adducts. The available theoretical studies on the structures of nanotube oxide and dichlorocarbene adducts that involve either armchair or zigzag tube models, employed rather unsatisfactory methodology (see below). Owing to the large size of nanotubes, carefully chosen truncated models, appropriate for the problem being investigated, are required. One approach uses small nanotube fragments to simulate a full nanotube, but carries out computations at a relatively high level. The other approach uses the ONIOM technique, which treats part of the system at a high theoretical level but the rest of the system at a lower level. This strategy allows larger systems to be simulated at a practical computational cost. Thus, a recent ONIOM(B3LYP/6-31G*:AM1) study employed a C16 fragment (Figure 1a) for the high-level computation to

6]Radialenes Revisited

Abstract[6]Radialene (2d) and its hexa‐ (2a) and dodecamethyl (2c) derivatives were subjected to several novel chemical reactions. Pyrolysis of 2a under flash vacuum conditions provided a mixture of 1,5‐hydrogen shift products 9 and 10, and the benzocyclobutenes 5 and 6, produced by electrocyclization of an intermediate o‐xylylene derivative 7. At the higher end of the investigated temperature range (200−400 °C) the formation of cyclization products 11 was also observed. The hydrocarbon 2c isomerized to the benzocyclobutene 12 under these conditions. Photolysis at 254 nm converted 2c into a novel isomer that, according to X‐ray structural analysis, has the unusual twist configuration 14. Compound 2c was photoisomerized through photoinduced hydrogen shift reactions to 15, and the stable p‐xylylenes 16 and 17. Dichloro‐ and dibromocarbene add to 2d with formation of the rotaradialene anti adducts 19a and 19b, respectively, the structures of which were also established by X‐ray structural analysis. With dichlorocarbene, 2a provided the three dichlorocarbene adducts 20, 22, and 23, whereas methylenation with diiodomethane/trimethylaluminium afforded a complex product mixture from which the monoadduct 21 could be isolated. The analogous product 24 and the bisadduct 25 were obtained from 2c under the same conditions. Epoxidation of 2a with m‐chloroperbenzoic acid gave the monoadduct 26, together with higher epoxidation products, which, however, could not be separated. Depending on the reaction conditions, 2c could be oxidized with m‐chloroperbenzoic acid to give the epoxides 27, 28, and 29. Hydrochlorination of 2a gave a complex mixture of addition products, which was converted into the olefins 9 and 10 by base treatment, showing that the addition step takes place less regioselectively than previously assumed. With Fe2(CO)9, 2a was converted into the iron tricarbonyl complex 33 in poor yield. Repetition of the literature procedure for the preparation of 2a allowed the isolation of novel diastereomers of this oldest hexaradialene; according to NMR experiments the methyl substituents of this hydrocarbon are arranged as shown in the structure cccaca‐2a. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

ChemInform Abstract: Dehydrohalogenation of Adducts of Dichlorocarbene with Cyclooctene and Its Peripherally Cyclopropanated Analogues.

AbstractChemInform 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.

Dehydrohalogenation of adducts of dichlorocarbene with cyclooctene and its peripherally cyclopropanated analogs

Dehydrohalogenation of three isomeric adducts of dichlorocarbene with bicyclo[6.1.0]non-1-,-2-, and-4-enes under the action of potassiumtert-butoxide in DMSO was studied. In the course of dehydrohalogenation of the substrates under study, different isomerization processes, which were accompanied by repeated migrations of multiple bonds that formed, occurred depending on the structure of dichlorides, while no skeletal rearrangements were observed.

ChemInform Abstract: C61Cl2. Synthesis and Characterization of Dichlorocarbene Adducts of C60.

AbstractChemInform 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.

C 61Cl 2. Synthesis and characterization of dichlorocarbene adducts of C 60

Dichlorocarbene generated by pyrolysis of sodium trichloroacetate was found to add to C 60 in a benzene-diglyme mixed solvent. The products C 60CCl 2) n (n=1-3) were isolated by means of gel permeation chromatography eluted with toluene and characterized by FAB mass spectroscopy. The structure Of C 60(CCl 2) was determined by 13C NMR spectroscopy. The addition occurred at the 6-ring/6-ring junction, giving a cyclopropane structure.

Diels‐Alder adducts of 4‐chloro‐1,6‐dihydrophosphinine derivatives: A new precursor of 2‐phosphapropene

AbstractThe 4‐chloro‐1,6‐dihydrophosphinine derivatives, prepared as a mixture of 3‐ and 5‐methyl isomers from the thermolysis of dichlorocarbene adducts with 1‐R‐3‐methylphospholene oxide (R  Me, MeO, EtO, n‐PrO, i‐PrO), participate in Diels‐Alder reactions with dimethyl acetylenedicarboxylate and N‐phenylmaleimide. The former reactant is of special value since the 2‐phosphabicyclo[2.2.2]octa‐5,7‐diene framework is thermally labile and undergoes retrocycloaddition by a different path, eliminating the CP bridging unit as a low‐coordinate species. Thus, in the case of R  Me, the initial phosphine oxides (a mixture of isomers) have been reduced to the phosphines and these undergo straightforward fragmentations on heating at 50°C to produce 2‐phosphapropene. The reactions of this transient species with water and alcohols have been investigated. Unlike the case of stabilized phosphaalkenes, hydration occurs smoothly without catalysis to produce Me2P(O)H; addition of alcohols gives phosphinites, Me2POR. The structure of the Diels‐Alder adducts was confirmed by 31P, 1H, and 13C NMR spectroscopy. Each of the isomeric 1,6‐dihydrophosphinine oxides gives two diastereomeric adducts; partial separation of some of the resulting four‐component mixtures was achieved with silica gel chromatography.

Cyclopropanation of poly[(methylphenylsilanediyl)‐(Z)‐butenylene]. Synthesis and characterization of poly[(methylphenylsilanediyl)methylenecyclopropylenemethylene

AbstractPoly[(methylphenylsilanediyl)methylenecyclopropylenemethylene] (3a) was prepared by cyclopropanation of the CC double bonds of poly[(methylphenylsilanediyl)‐(Z)‐butenylene] (2a) by a Simmons‐Smith reaction. Alternatively, 3a was prepared by a Birch reduction of the dichlorocarbene adduct poly[(methylphenylsilanediyl)methylene(2,2‐dichloro‐1,3‐cyclopropanediyl)‐methylene] (4a). Both 3a and 4a show the characteristic absorptions in the 1H, 13C, and 29Si NMR, IR and UV spectra. Their molecular weight distributions, determined by GPC, are rather broad and their thermal stabilities (by TG) are relatively high.

Some transformations of adducts of dichlorocarbene and 7-substituted benzonorbornadienes

It was observed in the present study that the addition of dichlorocarbene to benzonobornadiene under phase-transfer catalysis conditions permitted the isolation of the exo adduct, which underwent isomerization to the exo allylic chloride only upon prolonged storage, or upon distillation

ChemInform Abstract: Ring Transformations of Phosphorus‐Containing Heterocycles. Part 3. Reactivity of Phospholene Dichlorocarbene Adducts: Ring Expansion Effected by Mercury Acetate.

AbstractTreatment of the 3‐phosphabicyclo(3.1.0)hexane 3‐oxides (Ia) and (Ib) with mercury acetate (II) in acetic acid causes cleavage of the cyclopropane ring, forming the diastereo‐ and regioisomeric phosphorin 1‐oxides (III) and (IV).

ChemInform Abstract: Ring Transformations of Phosphorus‐Containing Heterocycles. Part 4. Synthesis of Dihydrophosphorins by Thermal Transformation of Phospholene Dichlorocarbene Adducts.

AbstractThe phospholene dichlorocarbene adducts (I) are thermally dehydrochlorinated to form mixtures of the regioisomeric dihydrophosphorin 1‐oxides (II) and (III).

EPR study of photoreduction of adducts of 3,6-di-tert-butyl-o-benzoquinone with dichlorocarbene

1. The formation of neutral and anion-radical particles was shown during the photoreduction of adducts of dichlorocarbene with 3,6-di-tert-butyl-o-benzoquinone in inert media and in the presence of amines, respectively. 2. The presence of thermo- and photoisomerization was shown for two forms of a neutral radical formed during the photoreduction of an adduct of 3,6-di-tert-butyl-o-benzoquinone with two dichlorocarbene fragments, consisting in opening of a three-membered ring with the formation of α,α′-dichloroalkyl radicals.

ChemInform Abstract: Synthesis of 1,2,3,6‐Tetrahydrophosphorin 1‐Oxides and 1,2‐Dihydrophosphorin 1‐Oxides from 3‐Phospholene 1‐Oxide Dichlorocarbene Adducts.

AbstractReaction of the 6,6‐dichlorophosphabicyclohexane 1‐oxides (I) with silver nitrate in water or methanol (II) yields a mixture of the phosphacyclohexenes (III) and (IV).

Birch reduction of the dichlorocarbene adduct of poly(1,1-dimethyl-1-sila-cis-pent-3-ene)(Cl2C-I): synthesis and characterization of poly(1,1-dimethyl-3,4-methylene-1-sila-cis-pent-3-ene) CH2-I)

Birch reduction of the dichlorocarbene adduct of poly(1,1-dimethyl-1-sila-cis-pent-3-ene) (Cl2C-I) yields poly(1,1-dimethyl-3,4-methylene-1-sila-cis-pent-3-ene) (CH2-I) which has been characterized by 1H, 13C and 29Si NMR spectroscopy as well as by elemental analysis. The molecular weight distribution of CH2-I has been determined by GPC and its thermal stability by TGA. Its glass transition temperature was obtained by DSC.

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.