Cyclization reactions of ω-tosyloxy-1-alkynyl- and ω-tosyloxy-1-alkenylborates and their ω-halo analogues

The reaction of trialkylboranes with ω-tosyloxy-1-lithio-1-alkynes can induce transfer of an alkyl group from the boron atom to the alkynyl carbon atom with concomitant formation of four- through six-membered carbocycles via intramolecular displacement of the ω-tosyloxy group. The stereoselectivity of the reaction, however, is low (anti/syn≃1.6–1.7). The corresponding reaction of ω-halo- or ω-tosyloxy-1-alkenylborates also gives exocyclic alkenes via 1,2-migration-cyclization followed by dehydroboration. In the cases of cyclopropanation, cyclopropylcarbinyl-to-homopropargyl rearrangement rather than dehydroboration takes place. Diphenylzirconocene reacts similarly with 6-lithio-5-hexynyl tosylate to give phenylmethylenecyclopentane in 45% yield. On the other hand, attempts to induce a similar migration with phenyl derivatives of Y, V, Cr, and Mn have led to < 5–10% yields of the same cyclization product.     

Synthesen von ω-substituierten ω-Nitrocarbonsäureestern aus α-Nitrocycloalkanonen

Synthesis of ω-Nitroalkanoates Substituted in ω-Position from α-Nitrocycloalkanones α-Nitrocycloalkanones substituted in α-position by a functionalized alkyl residue underwent ring opening to the corresponding chain derivatives by intermolecular nucleophilic attack; ω-nitroalkanoates substituted in ω-position were obtained (Scheme 1). The so formed methyl 6-nitro-9-oxodecanoate ( 3 ) was used to prepare methyl 8-(2-methyl-1,3-dioxolan-2-yl)octanoate ( 15 ), an intermediate in the synthesis of the sex phermone of the honey bee.     

Bifunctional even-electron ions: 1—Fragmentation behaviour of ω-methoxy-, ω-hydroxy- and ω-chloro-oxonium ions

Bifunctional oxonium ions—generated from tertiary aliphatic alcohols containing an additional hydroxy, methoxy or chloro group at the end of an alkyl side-chain—do not markedly exhibit fragmentations typical of ordinary oxonium ions, but show as the main reactions those caused by functional group interaction, through-space interaction being the dominant factor. The main primary fragmentation is loss of the additional functional group X as HX, followed by loss of the side-chain originally separating the two functional groups, leading to carbonyl cations. This typical reaction sequence is initiated by proton migration from the oxonium moiety to the additional functional group. The reaction behaviour of the bifunctional ions is discussed. The lowest homologues show specific deviations from the general fragmentation behaviour.     

α,ω-Dihydroxyalkan-α,α-diphosphonsäuren durch Desaminierung von ω-Aminoalkandiphosphonsäuren

α,ω-Dihydroxyalkane-α,α-diphosphonic Acids by Desamination of ω-Aminoalkanediphosphonic Acids The title compounds represent a new group of complexing diphosphonic acids which are synthesized by desamination of ω-amino-α-hydroxyalkane-α,α-diphosphonic acids. In case of α,ω-dihydroxypropane-α,α-diphosphonic acid ( 1 ) a phosphonylated phostone is formed by dehydration. In contrast, the ω-phenyl drivative of ( 1 ) yields in a smooth reaction under the same conditions 2-hydroxy-5-phenyl-3-phosphono-1.2-oxaphosphol-3-en-2-oxide ( 6 ).     

Structural Factors Affecting the Basicity of ω-Pyridylalkanols, ω-Pyridylalkanamides and ω-Pyridylalkylamines

The present paper describes the preparation by conventional methods (when not available commercially) and the pK_a-determination of the α-, β- and γ-isomers of pyridylethanamide, 3-pyridylpropanamide. 4-pyridylbutanamide, 5-pyridyl-pentanamide, pyridylmethanol, 2-pyridylethanol, 3-pyridylpropanol, 4-pyridyl-butanol, 5-pyridylpentanol, pyridylmethylamine, 2-pyridylethylamine, 3-pyridyl-propylamine, 4-pyridylbutylamine, and 5-pyridylpentylamine. While a field effect accounts for many variations in pK_a as a function of chain length, marked inductive effects are operative in some methyl and ethyl homologs. The pK_a-decreasing influence of an intramolecular H-bond is also apparent in some lower homologs belonging to the α-series.     

Coordination polymerization of ω-alkenoates and ω-epoxyalkanoates

As functional polymers have become more and more used, the need for a general synthesis of addition polymers with functional groups became greatly important. We have achieved the polymerization of ω-alkenoates with coordination initiators of the Ziegler-Natta initiation type using titanium trichloride-based transition metal initiators modified with dialkylaluminum chloride. To accomplish this polymerization required that the ω-alkenoates be precomplexed with dialkylaluminum chloride. High molecular weight homopolymers and copolymers with olefins have been obtained. The polymerization of ω-epoxyalkanoates with coordinative anionic polymerization systems based on triethylaluminum/water/acetylacetone (1.0/0.5/1.0) has also been accomplished. Homo- and copolymers of high molecular weight and of relatively narrow molecular weight distribution have been prepared. All polymers and copolymers of functional olefins and epoxides have been characterized and the study of the reactivity of the functional groups attached via a flexible spacer to the polymer main chain has been started. Special attention was given to the classical cationic copolymerization of trioxane with derivatives of ω-epoxyundecanoate to prepare novel functional polyoxymethylenes of potential commercial interest.     

Time-resolved ESR and endor during the photolysis of ω,ω-dimethoxy-ω-phenyl-acetophenone

The ketone ω,ω-dimethoxy-ω-phenyl-acetophenone (DMPA) is an efficient initiator in UV-curing polymerization processes started by photochemically generated radicals. The short-lived radical intermediates created during the photolysis of DMPA have been investigated by time-resolved ESR and ENDOR spectroscopy taking advantage of a strong CIDEP effect.     

Preparation of α,ω-ditriazinylperfluoroalkane derivatives

The synthesis of 2-oxa and 2-thiaperfluoroglutaric acids and their corresponding ethyl esters, amides, nitriles, acid chlorides, and also 2-thiaperfluoroglutaric anhydride are described. These compounds were prepared as precursors to α,ω-ditriazinylperfluoroalkane derivatives containing a heteroatom in the perfluoroalkylene chain. The ditrazinylpropanes were prepared most satisfactorily from the diacid chlorides rather than the dinitriles.     

Factors Influencing the Course of the Macrocyclization of α,ω‐Diamines with Esters of α,ω‐Dicarboxylic Acids

The efficient synthesis of eight new macrocyclic amides (lactams) via reaction of diesters with diamines under normal dilution conditions is described. The role of intermolecular H‐bond formation and steric hindrance is discussed based on ¹H‐ and ¹⁵N‐NMR studies of appropriate model compounds. Principles for the optimal choice of esters that can be efficiently transformed into diamides have been developed.     

Darstellung und Charakterisierung von α,ω-Dihydroperchloroligosilanen

Preparation and Characterization of α,ω-Dihydroperchloro Silanes Synthesis for the new compounds H(SiCl₂)_nH, n = 3?7 and HSi₄Cl₅ were described, starting from the perphenylated cyclosilanes. The new compounds were characterized and ¹H- and ²⁹Si-NMR spectra are discussed.     

α,ω-diols from polymerization of ethylene

Polyethylene is prepared in silver perchlorate solution by initiation with dialkyl peroxydicarbonates at 0–40°C. Saponification of the polymer endgroups yields a product rich in α,ω-diols. Well-known reactions convert the hydroxyl groups to other functional groups. The diol may be condensed with phosgene so as to increase its molecular weight severalfold or crosslinked with silicon tetrachloride to form a network.