Pyrolysis of homoadamant-3-ene

Pyrolysis of homoadamant-3-ene ($\text{5}$), generated from 1-adamantylcarbene ($\text{7}$), leads to the same three olefins ($\text{2}$, $\text{3}$, and $\text{4}$) that are produced from pyrolysis of 3-homoadamantyl acetate ($\text{1}$).     

Acid catalyzed isomerization of bicyclic alkenes: a facile betweenanene synthesis

Isomerization of $\text{cis}$-bicyclo[10.8.0]eicos-1(12)-ene ($\text{1a}$) and $\text{cis}$-bicyclo[10.10.0]docos-1(12)-ene ($\text{1b}$) to [10.8]- and [10.10]betweenanene ($\text{2a}$ and $\text{2b}$) has been effected by sulfuric acid. In both cases, the betweenanene isomers were found to predominate at equilibrium (70/30 $\text{2a}$/$\text{1a}$ and 95/5> $\text{2b}$/$\text{1b}$).     

A novel deaminative cyclization of aminoglycoside. Synthesis of a kanamycin B variant having 2-oxa-5-azabicyclo[2,2,2]oct-1,5-diene ring

The 3′,5′-diene derivative of kanamycin B ($\text{2}$) was obtained from a 4′-ene derivative of kanamycin B ($\text{1}$) by treatment with trimethyl orthoacetate. Formation of the title compound ($\text{4}$) from $\text{2}$ deaminative cyclization with sodium methoxide followed by treatment with trifluoroacetic acid was described.     

The photodecomposition of platinacycloalkanes in solution: II. 1,4-butanediylplatinum(II) and (IV) compounds

The products of the photolysis of a number of platinacyclopentanes in solution at 25°C under a variety of conditions have been determined. With [I₂P$\text{tCH}{}_2\text{CH}{}_2\text{CH}{}_2\text{C}$H₂(L₂)] (L = PMe₂Ph, PPh₃) in CH₂Cl₂, CH₂Br₂ and (CH₃)₂SO the hydrocarbon products are exclusively ethylene and but-1-ene. Formation of the latter through a 1,3-hydrogen shift is preceded by phosphine ligand dissociation. The photolysis of [ICH₃P$\text{tCH}{}_2\text{CH}{}_2\text{C}$H₂(L₂)] gave methane, ethylene, but-1-ene and n-pentane together with a little n-butane, the methane being formed from internal hydrogen abstraction by the CH₃ group in the excited reactant molecule. Photodecomposition of the platinum(II) compounds [P$\text{tCH}{}_2\text{CH}{}_2\text{CH}{}_2\text{C}$H₂(L₂)] (L = (PMe₂Ph)₂, (PPh₃)₂, Ph₂PCH₂CH₂PPh₂) gave ethylene, but-1-ene, pent-1-ene (with the halogenated solvents) and with some systems appreciable yields of n-butane, the latter being the results of internal abstraction of two hydrogen atoms by the C₄H₈ moiety. The formation of pentene is probably preceeded by the addition of CH₂Cl₂ or CH₂Br₂ to the excited reactant molecule. Addition of diphenylphosphine promotes the production of n-butane.     

The 185-nm photochemistry of 2,3-diazabicyclo[2.2.1]heptene and of its denitrogenation products bicyclo[2.1.0]pentane and cyclopentene

The 185-nm denitrogenation of 2,3-diazabicyclo[2.2.1]heptene ($\text{1}$) afforded bicyclo[2.1.0]-pentane ($\text{2}$) and cyclopentene ($\text{3}$) presumably via a “hot” cyclopentane-1,3-diyl diradical ($\text{8}$); 1,4-pentadiene ($\text{4}$) and methylenecyclobutane ($\text{5}$) were secondary products of the 185-nm photolysis of ($\text{2}$) and ($\text{3}$).     

Revision of an enamine synthesis; the preparation and reactions of 2-morpholinoisoflav-3-ene.

The condensation of $\text{N}$-styrylmorpholine with salicylaldehyde does $\text{not}$ give a product that can be oxidised to isoflavone; the product is $\text{N}$-morpholino-isoflav-3-ene which can be used to prepare other compounds related to isoflavan and upon oxidation gives 3-phenylcoumarin.     

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.     

Stekeospecific transformation of D-sugar to L-sugar in complex aminoglycoside. Synthesis of a kanamycin B analog having 2,6-diamino-2,4,6-trideoxy-L-arabino-hexopyranose

A 4′-ene derivative of kanamycin B ($\text{4}$) was derived from the epoxide ($\text{1}$) by oxidative elimination of the 4′-phenylseleno group into the allylic alcohol ($\text{3}$). The title compound, 0-(2,6-diamino-2,4,6-trideoxy-β-L-arabino-hexopyranosyl)-(1→4)-0-[3-amino-3-deoxy-α-D-glucopyranosyl-(1→6)]-2-deoxystreptamine ($\text{6}$) was obtained from $\text{4}$ by stereospecific hydrogenation followed by removal of the masking groups, changing the D-sugar moiety of the 4-0-glycoside portion into an L-sugar.     

Ritter-reaction on steroids: Ring expansion of steroid oxethans into dihydrooxazines

The 3β-acetoxy-16β,17β-epoxymethyleneandrost-5-ene ($\text{1}$) transforms into the dihydrooxazine condensed to the sterane skeleton ($\text{4}$$\text{a}$,$\text{b}$,$\text{c}$,$\text{e}$,$\text{g}$,$\text{i}$) in a ring-expansion reaction with alkyl and aryl nitriles in the presence of HBF₄— diethyletherate The 3β-acetoxy-16α, 17α-epoxymethyleneandrost-5-ene ($\text{9}$) undergoes a Wagner-Meerwein rearrangement under similar conditions.     

Formation and trapping of 6-azabicyclo[3.2.2]non-5-ene,a strained bridgehead imine

Photolysis or flash vacuum pyrolysis of 1-bicyclo[3.2.1]octylazide $\text{9}$ yields 6-azabicyclo[3.2.2]non-5-ene $\text{10}$, a strained bridgehead imine, which could not be isolated but was trapped with methanol.     

Chiral discrimination in the reactions of the enolate E-[(η5-C5H5)Fe(CO)(PPh3)COCHMe]−Li+ with cis and trans but-2-ene oxides in the presence of BF3·OEt3

$\text{cis}$ and $\text{trans}$-but-2-ene oxides undergo S_N2 opening with the lithium enolate derived from [(η⁵-C₅H₅)Fe(CO)(PPh₃)COCH₂CH₃] in the presence of BF₃·OEt₂; preferential opening occurs where the enolate configuration at iron matches that of the epoxide carbon being attacked.     

Generation and reactivity of bis(2,6-diethylphenyl)germanium(II)

The title intermediate ($\text{3a}$) is produced on photolysis of hexakis(2,6-diethyl-phenyl)cyclotrigermane ($\text{1}$) or bis(2,6-diethylphenyl)bis(trimethylsilyl)germane ($\text{4}$) as evidenced by trapping experiments, and thermally dimerizes to tetrakis(2,6-diethyl-phenyl)digermene ($\text{2a}$). Diarylgermylenes such as $\text{3a}$ do not form stable triethylamine adducts (e.g. $\text{5a}$) as has been previously reported.     

Condensed cyclic and bridged-ring systems : part 12: A novel synthetic route to 4-p-methoxyphenyl-bicyclo[ 2.2.2 ]octan-2-ones and some bicyclo [ 3.2.1 ] octane derivatives by acid-catalyzed intramolecula

The efficacy of a new acid-catalyzed intramolecular C-alkylation has been demonstrated by the synthesis of 1-methyl-4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{5}$) and 4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{6}$) from easily accessible starting materials. The carbinol $\text{20}$, derived from $\text{5}$, undergoes facile rearrangement leading to 1-$\text{p}$-methoxyphenyl-4-methyl bicyclo [3.2.1] oct-3-ene ($\text{22}$), which has been transformed to $\text{endo}$-1-$\text{p}$-methoxyphenyl-4-methylbicyclo [3.2.1] octan-3-one ($\text{25}$).     

v-Triazolines. part XXI. Spiro[bicyclo[2.2.1]hept-2-ene[54']1',2'.s'-triazole]derivatives from cyclopentadiene and 5-amino-4-methylene-v-triazolines

1R^*, 4R^*, 5S^*, 5'S^*-5'-Amino-1'-(4-nitrophenyl)-4',5'-dihydrospiro[bicyclo [2.2. 1]hept-2-ene[5.4]-1',2',3'-triazoles]$\text{2}$ have been obtained both by ?4 +2]-cycloaddition of cyclopentadiene to amino-methylene-1-(4-nitrophenyl)-4,5-dihydro-v-triazoles $\text{1}$ and by [3+2]-cycloaddition of 4-nitrophenylazide to 5-aminomethylene-2-norborenes $\text{4}$. The configuration has been fully established by X-ray crystallographic analysis. The course of the cycloaddition and the thermal behaviour of $\text{2}$ are discussed.     

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°.     

Convenient new synthesis of snoutene [1] utilizing a dipolar cycloaddition of 4-phenyl-1,2,4-triazolin-3,5-dione

4-Phenyl-1,2,4-triazolin-3,5-dione readily cycloadds to Nenitzescu's hydrocarbon $\text{1}$^[6] with skeletal rearrangement. The major adduct $\text{6}$ can conveniently be transformed to the azo compound $\text{8}$, which upon photolysis or thermolysis yields up to 80 % pentacyclo[3.3.2.0^2,4,.0^3,7.o^6,8]dec-9-ene (“ snoutene ”).     

The fluorinations of pentafluoronitrobenzene and pentafluorobenzaldehyde by cobalt(III) fluoride

The nitro-group survived in the fluorination of pentafluoronitrobenzene by cobalt(III) fluoride at 135–150°, the major products being undecafluoronitrocyclohexane and nonafluoro-4-nitrocyclohex-1-ene. 2H- Tetrafluoronitrobenzene similarly afforded $\text{cis-}$ and $\text{trans}$-2H-1-nitrodeca- fluorocyclohexane and 5H/4-nitro-octafluorocyclohex-l-ene. Pentafluoro- benzaldehyde was fluorinated to give undecafluorocyclohexanecarbonyl fluoride and nonafluorocyclohex-3-enecarbonyl fluoride. Nonafluoro-4- nitrocyclohex-1-ene was oxidized to 3-nitroheptafluorohexan-1,6-dioic acid, and undecafluoronitrocyclohexane was hydrogenated over a palladium catalyst at low pressure to give decafluorocyclohexanone oxime and 1H-decafluoro- cyclohexanamine, accompanied by 1-aminononafluorocyclohex-1-ene.     

Synthesis of 4, 8-dihydroxy-3-methyl-5,6-benzo-2-oxabicyclo[2.2.2]oct-5-ene

The title compound having the same relative configurations as granaticin($\text{1}$) and U-58,431($\text{2}$) was prepared either by dehydrogenative cyclization of the precursor $\text{9a}$ or by pinacol cyclization of the dicarbonyl compound $\text{15}$.     

Yield of I(2Psol:12) in the photodissociation of CH2I2

The production of I(²P_{$\text{1}\text{2}$}) in the photolysis of CH₂I₂ has been studied optoacoustically at excitation wavelengths between 365.5 and 247.5 nm. Bands found at 32200 and 47000 cm^?1 correlate with I(²P_{$\text{3}\text{2}$}) whilst those at 34700 and 40100 cm^?1, which correlate with I(²P_{$\text{1}\text{2}$}), give final ²P_{$\text{3}\text{2}$}/²P_{$\text{1}\text{2}$} ratios of 1.75 and 1.1, respectively, after curve crossing.