Herstellung der reinen,bicyclischen Olefine Bicyclo[4.2.1]non-2-en,Bicyclo[4.2.1]non-3-en und Bicyclo[4.2.1]non-7-en

Synthesis of the pure, bicyclic olefines Bicyclo[4.2.1]non-2-ene, Bicyclo[4.2.1]non-3-ene and Bicyclo[4.2.1]non-7-ene The synthesis of the olefines bicyclo[4.2.1]non-2-ene ( 3 ), bicyclo[4.2.1]non-3-ene ( 4 ) and bicyclo[4.2.1]non-7-ene ( 5 ) of high ‘certified’ purity from one common precursor ( 7 ) is described.     

Synthesis of Bridged Bicyclic Molecules using Halocarbenes. Derivatives of bicyclo[4.2.1]nonane

The addition of dichlorocarbene (generated by the interaction of sodium methoxide and ethyl trichloroacetate) to bicyclo[3.2.1]oct-2-ene, its 3-chloro and exo-3,4-dichloro derivatives gives the exo 1 : 1 adducts in yields of 94, 89 and 48%. By suitable chemical reactions of these adducts, convenient syntheses of bicyclo[4.2.1]nona-2,4-diene and bicyclo[4.2.1]non-3-ene, together with their monochloro, dichloro and trichloro derivatives are obtained. Bicyclo[4.2.1]-nonan-3-one is also obtained from bicyclo[4.2.1]non-3-ene in a synthesis starting from the readily available 5-hydroxymethylnorborn-2-ene in an overall yield of 20%.     

A facile synthesis of strained bridgehead olefins by a gas-phase elimination reaction

A synthesis of bicyclo[3.3.1]non-1-ene $\text{1}$ and of a 10:1 mixture of bicyclo[4.2.1]non-1(8)-ene $\text{2}$ and bicyclo[4.2.1]non-1(2)-ene $\text{3}$ by gas-phase pyrolysis of the corresponding bridgehead acetates and chlorides is reported.     

Thermotropic homopolyester. I. Synthesis and characterization of homopolyesters containing the mesogenic unit,bicyclo[2.2.2]oct-2-ene

Homopolyesters based on bicyclo[2.2.2]oct-2-ene as a mesogenic group were prepared and characterized. The use of bicyclo[2.2.2]oct-2-ene in these homopolyesters lowered the symmetry of the resulting systems enough to lead to the observation of melting behavior.     

[2 + 2]-Cycloadditions to Strained Bridgehead Olefins. II. Diphenylketene

The strained bridgehead olefins bicyclo [3.3.1]non-1-ene ( 1 ), bicyclo [4.2.1 ]non-1(8)-ene ( 2 ), and bicyclo [4.2.1]non-1-ene (3), and the comparable monocyclic (E)-1-methylcyclooctene ( 4 ) react with diphenylketene ( 6 ) to give a single cycloadduct 7 , 8 , 9 and 10 , respectively, in which the diphenyl-substituted C-atom is bound to the bridgehead. The structure of the cyclobutanone 8 has been determined by X-ray analysis of a twin crystal obtained by crystallization with spontaneous enrichment of enantiomers.     

Bicyclo[3.1.0]hex-(1,5)-ene and bicyclo[4.1.0]hept-(1,6)-ene

The formation and trapping of bicyclo[3.1.0]hex-(1,5)-ene and bicyclo[4.1.0]hept-(1,6)-ene from the corresponding vicinal dibromides is described.     

Thermal reactions of 7-d- and 8-d-bicyclo[4.2.0]oct-2-enes

The gas phase thermal reactions exhibited by bicyclo[4.2.0]oct-2-ene and 7-d and 8-d analogues at 300 degrees C have been followed kinetically through GC and 2H NMR spectroscopic analyses. In contrast to the pattern of transformations exhibited by bicyclo[3.2.0]hept-2-ene and deuterium-labeled analogues, no reactions initiated by C1-C6 bond cleavage are seen, epimerization at C8 is much faster than [1,3] shifts leading to bicyclo[2.2.2]oct-2-ene, and the ratio of rate constants for [1,3] carbon migration with inversion versus migration with retention is approximately 1.4. Homolysis of C1-C8 to give a conformationally flexible diradical intermediate having a relatively long lifetime and multiple options for further reaction (re-formation of C1-C8 with or without net epimerization, fragmentation to 1,3-cyclohexadiene and ethylene, migration to the original C3 with inversion or retention) accords well with the observations. Clearly, orbital symmetry control does not govern stereochemistry for the [1,3] sigmatropic carbon shifts.     

1,3-Dipolar Cycloadditions to Strained Olefins

The Bredt olefins bicyclo [3.3.1]non-1-ene (2) , bicyclo [4.2.1]non-1 (8)-ene (3) , and bicyclo [4.2.1]non-1 (2)-ene (4) react rapidly with 1,3-dipoles such as diazomethane, phenyl azide, and mesitonitrile oxide to yield mixtures of two regioisomeric cycloadducts 10, 11 and 12 , respectively. On the contrary, cycloaddition to the comparable monocyclic 1-methyl-(E)-cyclooctene (5) is fairly regioselective. 2-Methylnorborn-2-ene (6) gives one isomer with mesitonitrile oxide (as do less strained olefins), but mixtures with diazomethane and phenyl azide. ¹H-NMR. and ¹³C-NMR. spectra of the cycloadducts are reported. The results are discussed in the light of frontier molecular orbital theory.     

Synthesis of monoethers by addition of aliphatic diols to bicyclo[2.2.1]hept-2-enes

Addition of aliphatic diols to bicyclo[2.2.1]hept-2-ene and its 5-alkyl-substituted derivatives in the presence of naphthalene-1,5-disulfonic acid leads to the formation of the corresponding bicyclo[2.2.1]hept-2-yl monoethers in high yields.     

[2 + 2]-Cycloadditions to Strained Bridgehead Olefins. I. 1, 1-Dichloro-2,2-difluoroethene

The strained bridgehead olefins bicyclo [3.3.1]non-1-ene ( 1 ), bicyclo [4.2.1] non--1-(8) ( 2 ), and bicyclo [4.2.1]non-1-ene ( 3 ) react rapidly with 1,1-dichloro-2, 2--difluoroethene ( 5 ) to yield mixtures of regioisomeric dichlorodifluorocyclobutanes 8/9, 10/11 and 12/13 , respectively. On the contrary, the reaction of 5 with the model compound (E)-l-methylcyclooctene ( 4 ) is completely regioselective. The structure of the cycloadducts has been elucidated mainly by ¹⁹F-NMR. and ¹³C-NMR. spectroscopy.     

Electronic and Steric Structure of Thermal Isomerization Products of 1-Methyltricyclo[4.1.0.02,7]heptane Radical Cation

Distributions of the positive charge and unpaired electron in stable conformers of the thermal isomerization products of 1-methyltricyclo[4.1.0.02,7]heptane radical cation, having bicyclo[3.1.1]heptane, bicyclo[4.1.0]heptane, bicyclo[3.2.0]hept-6-ene, and 1,3-cycloheptadiene skeletons, were estimated by the PM3 semiempirical method.     

[2+2]-cycloadditions of cyclopentyne

Cyclopentyne, as generated from dibromomethylenecyclobutane, a formerly unknown cyclopentyne source, undergoes [2+2]-cycloadditions with various substituted olefins yielding bicyclo[3.2.0]hept-1(5)-ene derivatives.     

Thermal chemistry of bicyclo[4.2.0]oct-2-enes

At 300 degrees C, bicyclo[4.2.0]oct-2-ene (1) isomerizes to bicyclo[2.2.2]oct-2-ene (2) via a formal [1,3] sigmatropic carbon migration. Deuterium labels at C7 and C8 were employed to probe for two-centered stereomutation resulting from C1-C6 cleavage and for one-centered stereomutation resulting from C1-C8 cleavage, respectively. In addition, deuterium labeling allowed for the elucidation of the stereochemical preference of the [1,3] migration of 1 to 2. The two possible [1,3] carbon shift outcomes reflect a slight preference for migration with inversion rather than retention of stereochemistry; the si/sr product ratio is approximately 1.4. One-centered stereomutation is the dominant process in the thermal manifold of 1, with lesser amounts of fragmentation and [1,3] carbon migration processes being observed. All of these observations are consistent with a long-lived, conformationally promiscuous diradical intermediate.     

The Non-planarity of the Bicyclo[2.2.1]hept-2-ene Double bond. Crystal Structures of Bicyclo[2.2.2]oct-2-ene,Bicyclo[2.2.1]hept-2-ene,and Bicyclo[2.1.1]hex-2-ene Systems

The crystal structures of (1R,4R,5S,8S)-9,10-dimethylidentricyclo[6.2.1.0^2,7]undec2(7)-ene-4,5-dicarboxylic anhydride ( 3 ), (1R,4R,5S,8S)11-isopropylidene-9,10-dimethylidenetricyclo[6.2.1.m^2,7]undec-2(7)-ene-4,5-dicarboxylic anhydride ( 6 ), (1R,4R,5S8S)-9,10-dimethylidenetricyclo[6.2.2.0^2,7]dodec-2(7)-ene-4,5-dicarboxylic anhydride ( 9 ), (1R4R5S8S)-TRICYCLO[6.2.2.0^2,7]dodeca-2(7), 9-diene-4,5-dicarboxylic anhydride ( 12 ) and (4R,5S)-tricyclo[6.1.1.0^2.7]dec-2(7)-ene-4,5-dicarboxylic acid ( 16 ) were established by X-ray diffraction. The alkyl substituents onto the endocyclic bicyclo[2.2.1]hept-2-ene double bond deviate from the C(1), C(2), C(3), C(4), plane by 13.5°4 in 3 and by 13.9° in 6 , leaning toward the endo-face. No such out-of-plane deformations were observed with the bicyclo[2.2.2]oct-2-ene derivatives 9 and 12 . The exocyclic s-cis-butadiene moieties in 3, 6 and 9 do not deviate significantly from planarity. The deviation from planarity of the double bond n bicyclo[2.2.1]hept-2-ene derivatives and planarity in bicyclo[2.2.2]oct-2-ene analogues is shown to be general by analysis of all known structures in the Cambridge Crystallographic Data File. The non-planarity of the bicyclo[2.2.1]hept-2-ene double bond cannot be attributed only to bond-angle deformations which would favour rehybridizatoin of the olefinic C-atoms since the double bond in the more strained bicyclo[2.1.1]hex-2-ene drivative 16 deviates from planarity by less than 4°.     

Umsetzungen des Cyclohex-3-en-carbaldehyd-p-toluolsulfonylhydrazons

The vacuum thermolysis (80–90°) of the sodium salt of cyclohex-3-ene-carbaldehyde p-toluenesulfonylhydrazone ( 1 ) in silicone oil gave diazomethyl-cyclohex-3-ene ( 2 ). Pyrolytic and photolytic decomposition of this diazo compound 2 lead to methylenecyclohex-3-ene ( 5 ) and bicyclo [4.1.0]hept-2-ene ( 6 ) (about 3:1), while the CuCl catalyzed cleavage yielded only 5 . The postulated carbene mechanism should also apply under the direct aprotic decomposition conditions of the sodium salt of 1 in diglyme, where methylenecyclohex-3-ene and bicyclo[4.1.0]hept-2-ene (about 3:1) were formed besides small amounts of 1-methylcyclohexa-1, 3-diene ( 9 ) and bicyclo [4.1.0]hept-3-ene ( 8 ). Under protic conditions (in ethylene-glycol) methylenecyclohex-3-ene, 1-methylcyclohexa-1, 3-diene and 1-methylcyclohexa-1, 4-diene ( 14 ) were produced in a ratio of 1:1:1. The direct mild thermolysis of cyclohex-3-ene-carbaldehyde p-toluenesulfonylhydrazone ( 1 ) in benzene solution afforded N-(p-toluenesulfinyl)-O-(p-toluenesulfinyl)-cyclohex-3-en-yl-α-methanolamine ( 15 ) and di-(cyclohex-3-en-yl-methyl)-ammonium p-toluenesulfonate ( 16 ), the structures of which were supported by their nmr. spectra and by alkaline cleavage.     

Maximum-overlap hybridization in bicyclo [2.1.0] pent-2-ene

Applying the method of maximum overlap, the hybridization in bicyclo[2.1.0]pent-2-ene is determined. In addition, upon comparing these results with those of cyclobutene, cyclopropane, Dewar benzene and bicyclo[1.1.0]butane, it is found that the hybrids calculated by the method of maximum overlap are transferable between parts of molecules for which the structural features are similar.     

The Synthesis and Chemistry of 8-Substituted Bicyclo[5.1.0]oct-1(8)-ene

8-Bromobicyclo[5.1.0]oct-1(8)-cne (7), an intermediate for the preparation of 8-substituted bicyclo[5.1.0]oct-1(8)-enes, was synthesized by denomination of 1,8,8-tribromobicyclo[5.1.0]octane (6). Compound 7 underwent bromo-lithium exchange followed by nucleophilic substitution reactions to generate bicyclo[5.1.0]oct-1(8)-ene (5), 8-methylbicyclo[5.1.0]oct-1(8)-ene (10), and 8-trimethylsilylbicyclo[5.1.0]oct-1(8)-ene (11). The bicyclic cyclopropenes 7, 5, 10, and 11 reacted with cyclopentadiene to form adducts 12, 13, 14, and 15, respectively. All of these Diels-Alder adducts are endo-exo isomers (endo-addition from the view of the cyclopropene and exo-addition from the view of the cyclooctene).     

Addition von organomagnesium-verbindungen an nicht aktivierte CC-doppelbindungen : IV. Benzylmagnesiumchlorid und olefine

Benzylmagnesium chloride (I) adds to ethylene and 1-alkenes, to the strained CC double bonds in bicyclo[2.2.1]hept-2-ene and bicyclo[2.2.1]heptadiene and to 1,3-alkadienes if the reaction of the etherate of (I) with olefin is carried out in an apolar reaction medium between 60 and 130°. Reaction products of the mono-olefins are the 1,1-adducts; derivatives of divinylcyclohexane are formed with butadiene as 1,3-adducts. With bicyclo[2.2.1]heptadiene the addition of the magnesium compound is followed by an intramolecular MgC-addition to the second double bond forming 2-benzyltricyclo[2.2.1.0¹]hept-3-ylmagnesium chloride.     

Thermal isomerization of tricyclo[4.1.0.0(2,7)]heptane and bicyclo[3.2.0]hept-6-ene through the (E,Z)-1,3-cycloheptadiene intermediate

The thermal isomerization of tricyclo[4.1.0.0(2,7)]heptane and bicyclo[3.2.0]hept-6-ene was studied using ab initio methods at the multiconfiguration self-consistent field level. The lowest-energy pathway for thermolysis of both structures proceeds through the (E,Z)-1,3-cycloheptadiene intermediate. Ten transition states were located, which connect these three structures to the final product, (Z,Z)-1,3-cycloheptadiene. Three reaction channels were investigated, which included the conrotatory and disrotatory ring opening of tricyclo[4.1.0.0(2,7)]heptane and bicyclo[3.2.0]hept-6-ene and trans double bond rotation of (E,Z)-1,3-cycloheptadiene. The activation barrier for the conrotatory ring opening of tricyclo[4.1.0.0(2,7)]heptane to (E,Z)-1,3-cycloheptadiene was found to be 40 kcal mol(-1), while the disrotatory pathway to (Z,Z)-1,3-cyclohetpadiene was calculated to be 55 kcal mol(-1). The thermolysis of bicyclo[3.2.0]hept-6-ene via a conrotatory pathway to (E,Z)-1,3-cycloheptadiene had a 35 kcal mol(-1) barrier, while the disrotatory pathway to (Z,Z)-1,3-cyclohetpadiene had a barrier of 48 kcal mol(-1). The barrier for the isomerization of (E,Z)-1,3-cycloheptadiene to bicyclo[3.2.0]hept-6-ene was found to be 12 kcal mol(-1), while that directly to (Z,Z)-1,3-cycloheptadiene was 20 kcal mol(-1).     

Synthesis of esters by addition of chloroacetic acid to cage-like cyclic olefins

Thermal addition of chloroacetic acid to bicyclo[2.2.1]hept-2-ene, its 5-alkyl-substituted derivatives, and tricyclo[5.2.1.0^2,6]deca-3,8-diene gave the corresponding chloroacetic acid esters which attract interest as potential insecticides for plant protection.