Eine Synthese von Bicyclo[10.3.0]pentadec-1(12)-en-13-on und seinem 14-Methylderivat

A Synthesis of Bicyclo[10.3.0]pentadec-1(12)-en-13-one and its 14-Methyl Derivative. A new route to bicyclo[10.3.0]pentadec-1(12)-en-13-one ( 2 ) and its 14-methyl derivative 3 – useful intermediates in the synthesis of cyclopentadecanone ( 4 = exaltone®) and rac-muscone ( 5 ) – is described.     

Finite energy sum rules with the Cheng-representation

The unitary Cheng representation for the partial wave amplitudes is adopted to calculate the left-hand side of a FESR in theππ-system. The results confirm the nonsense choosing mechanism for theρ-meson and give a hint fort-dependence of the remaining residuum functionβ(t).     

Total Synthesis of (±)-Clovene. On the Stereoelectronic Requirements of the α-Alkynone Cyclisation

The synthesis of the sequiterpenoid tricyclic hydrocarbon (±)-cleovene ( 1 ) by application of the α-alkynone cyclisation is described. The starting bicyclic carboxylic acid 2 was obtained from ethyl 3-methyl-2-oxocyclohexane-1-carboxylate by modified known methods (24%) and converted to the α-alkynone 3 (86%). The thermolysis of 3 in the gas phase at 620° selectively produced the tricyclo[6.3.1.0^1,5] dodecenone 4 (80%) which was converted to 1 (37%) by conventional procedures. The selectivity of the α-alkynone cyclisation is discussed in terms of the stereoelectronic requirements (coplanarity factor) of the carbene insertion. In order to throw further light on the importance of this factor, the (1-adamantyl) alkynone 16 was synthesised from adamantane-1-carboxylic acid (78%) and subjected to thermolysis at 620°. Since this led to the tetracyclo[6.3.1.1.1^3,10.0^3,7]tridecenones 17 and 18 (together 72%), we conclude that the planar carbene insertion transition state, while preferred, is not a stringent requirement.     

Umwandlung der diastereomeren 12- und 6-gliedrigen 1-Acetyl-2-methyl-1-cycloalkanole in 1-Äthinyl-2-methyl-1-cycloalkene

Conversion of the Diastereoisomeric 12-and 6-membered 1-Acetyl-2-methyl-1-cycloalkanols to 1-Ethynyl-2-methyl-1-cycloalkenes This paper is concerned primarily with a derivation of the E-configuration of 1-ethynyl-2-methyl-1-cyclododecene ( 10 ), which plays a role in mechanistic considerations on a method for ring expansion by 3 carbon atoms described in apreceding paper [1]. The derivation is based on an argument using the results of the dehydration of trans-1-acetyl-1-2-methyl-1-cyclododecanol ( 4 ) to 10 with phosphorus oxychloride and pyridine. That this dehydration is stereospecific can be concluded from its regiospecificity since the cis-hydroxyketone 3 dehydrates mainly to 1-ethynyl-12-methyl-1-cyclododecene (mixture of stereoisomers 11 and 12 ). An x-ray analysis shows the indicated configurations of the two hydroxyketones 3 and 4 . The direction (anti) of the stereospecificity of the double bond introduction during the 4 → 10 conversion is deduced from the similarity of the behaviour of the two stereoisomeric 1-acetyl-2-methyl-1-cyclohexanols 8 and 9 under the same conditions and from mechanistic considerations, which make it likeley that the anti-elimination behaviour observed in the 6-membered system has not changed over to a syn-elimination behaviour in the 12-membered system. The configurations of the two 6-membered hydroxyketones 8 and 9 correspond to those of the precursor1-ethynyl-2-methyl-1-cyclohexanols 6 and 7 , which were clarified with the help of ¹³C-NMR.-spectral coupling observations. It is of interest that the hydroxyketones 3, 4, 8 and 9 react with phosphorus oxychloride and pyridine so as to introduce both a double and a triple bond. It is probable that the double bond is introduced first, inasmuch as the triple bond is not introduced in the absence of activation of the hydroxyl group, as for instance in acetylcyclohexane. This can be used as an argument that the conversion of the acetyl to an ethynyl group in 3, 4, 8 and 9 does not affect the stereospecificity of the dehydration which introduces the ring double bond. 1-Acetyl-2-methyl-1-cyclododecene ( 24 ), a previously isolated compound with pleasant odor, was synthesized by hydration of 10 . This furnishes an argument for the E-configuration of 24 .     

Butanolide und Butenolide durch intramolekulare En-Reaktion bei der Thermolyse von Propargyl-propiolaten

Butanolides and Butenolides by Intramolecular Ene-Reaction during Thermolysis of Propargyl Propiolates Gas-phase flow thermolysis of 2-butynyl propynoate ( 1 ) and 2-propynyl 2-butynoate ( 2 ) at 550° afforded 3-ethynyl-2-methyl-2-buten-4-olide ( 4 , 85%) and 2-ethynyl-3-methyl-2-buten-4-olide ( 5 , 80%), respectively. Their formation presumably entails an ene reaction between the methylacetylenic and the acetylenic functions of the diyne esters 1 and 2 to give the two methyliden-vinyliden-butanolides 10 and 11 as intermediates, followed by a [1,5]-H shift to 4 and 5 . At 400–450°, the gas phase flow thermolysis of 1 and 2 led to the dimers 16 (77%) and 17 (6%), respectively. These products resulted from the Diels-Alder dimerization of the above mentioned intermediates 10 and 11 . The regioselectivity of this dimerization is determined by a ‘head-to-head’ approach, with the double bond conjugated to the carbonyl group acting as the dienophile in both cases. The low yield of 17 from 2 is probably due to a further Diels-Alder reaction of the dimer 17 with its precursor 11 , yielding a trimer 18 (8% isolated). This process is not possible when starting with 1 , which explains the higher yield of 16 . The gas phase flow thermolysis of 2-butynyl 2-butynoate ( 3 ) at 550° afforded a mixture of four isomeric products, namely the two monocyclic ethynyl-butenolides 6 and 7 and the two bicyclic vinyl-butenolides 8 and 9 . The formations of 6–9 are also rationalizable by initial ene-reactions, in this case two alternative ones, each involving one of the two CH₃ groups of 3 . This leads to two alkylidene-vinylidene-butenolides, namely 12 and 13 . A [1,5]-H shift converts 12 into 6 and 13 into 7 . A competing alternative [1,5]-H shift transforms both 12 and 13 to the triene 14 , which electrocyclizes to the cyclohexadiene 15 . The latter undergoes two alternative [1,5]-H shifts to yield 8 and 9 .     

The acylation of acetylenes with β, γ-unsaturated acid chlorides: a new sysnthesis of 5,5-disubstituted 2-cyclopentenones

The acylation of acetylenes with α,α-disubstituted, β,γ-unsaturated acid chlorides was found to lead to 5,5-disubstituted 2-cyclopentenones bya novel intramolecular cyclization-rearrangement process.     

Radiative corrections toe + —e − scattering mediated by neutral vector bosons

Since it is very likely that the contributions (if there are any at all) of weakly interacting neutral vector bosons to ordinary Bhabha scattering can be increased sufficiently with respect to the common photon process, the weak coupling constant might be measured with great accuracy in these processes. Therefore it is necessary to know the amount of the radiative corrections to this process, which is calculated in this paper.