Photochemical studies. Irradiation induced transformations of 1,2-dihydrophthalides

The photochemical behavior of $\text{cis}$-1,2-dihydrophthalide ($\text{1}$) and its 1,2-trimethylene derivative ($\text{4}$) was studied. Besides bicyclo[2.2.0]hexene formation in both cases, ($\text{1}$) transforms into its $\text{trans}$ isomer ($\text{3}$) whereas ($\text{4}$) undergoes a 1,2-shift to ($\text{7}$).     

1,2-dimagnesium derivatives of cyclopropane

cis-1,2-Dibromomagnesiocyclopropane (cis-$\text{4}$) was isolated from the reaction of both trans- and cis-1,2-dibromocyclopropane ($\text{1}$) with magnesium. The corresponding dialkylmagnesium species ($\text{7}$), an oligomer of 2-magnesabicyclobutane, was obtained from cis-$\text{4}$ by precipitation in THF; it forms a soluble complex 8 with HgBr₂.     

The synthesis of cis- and trans-1,2-dibromocyclopropane

A preparative route to cis- and trans-1,2-dibromocyclopropane ($\text{1}$) was developed via the Hunsdiecker reaction of silver cyclopropane-1,2-dicarboxylate ($\text{2}$). Cis- and trans-$\text{2}$ gave the same ratio of cis- and trans-$\text{1}$ (1:3.2). The mechanism of this reaction is briefly discussed.     

Adamantane rearrangement mechanisms. 1,2-trimethylenenorbornanes

Unexpected differences in the aluminium bromide-catalyzed rearrangement behaviour of 1,2-$\text{endo}$-trimethylenenorbornane ($\text{1}$) and its 1,2-$\text{exo}$-isomer ($\text{2}$) are interpreted. Isotopic labelling studies indicate that reversible abstraction of the tertiary 2-$\text{endo}$ hydride in $\text{2}$ does not occur. Instead, rearrangement to $\text{6}$ is favored. The label scrambling in the final product, adamantane ($\text{8}$), is attributed to degenerate isomerization in the proto-adamantyl precursor, $\text{7}$.     

Reaction of benzothiazoline with benzyne - generation of novel heterocyclic sulfur ylide,benzothiazolinium s-ylide

A novel heterocyclic sulfur ylide, 2-t-butyl-3-methyl-1-phenylbenzothiazolinium ylide ($\text{13}$) was generated as an intermediate in the reaction of 2-t-butyl-3-(nethy1benzothiazoline ($\text{2}$) with benzyne. The S-ylide $\text{13}$ underwent a novel intermolecular [1,2] shift to give 2-t-butyl-3-methyl-2-phenylbenzothiazoline ($\text{4}$).     

Electron exchange chemiluminescence from a sterically stabilized cyclobutadiene-1,2-dioxetane

The rather stable 1,2-dioxetanes ($\text{2}$) and ($\text{3}$), derived from the sterically stabilized cyclobutadiene ($\text{1}$), exhibit distinct enhanced chemiluminescence behavior, namely energy transfer chemiluminescence (ETC) for ($\text{2}$) and electron exchange chemiluminescence (EEC) for ($\text{3}$).     

Synthesis of 2β-fluoro-1α-hydroxyvitamin D3

2β-Fluoro-1α-hydroxyvitamin D₃($\text{3}$) was prepared from 1,2α-epoxy-cholest-5-en-3β-yl tetrahydropyranyl ether($\text{1a}$ via 2β-fluorocholest-5-ene-1α, 3β-diol($\text{2}$).     

Singlet oxygenation of cycloheptatriene: isolation and characterization of the 1,2-dioxetane

Tetraphenylporphyrin-sensitized photooxygenation of cycloheptatriene afforded the 1,2-dioxetane ($\text{3a}$) in 9% yield, thus completing the set of possible cycloaddition products; the 1,2-dioxetane ($\text{3a}$) is the precursor to the benzaldehyde product, but not the (2+6)-cycloadduct ($\text{2a}$).     

Conformational dependence of pyranoid rings 1,2-cis-fused to dioxolane rings on the configuration of the dioxolane rings in acetylated derivati

X-Ray and ¹H N.M.R. studies on pyranoid rings 1,2-$\text{cis}$-fused to dioxolane rings in acetylated $\text{D}$-gluco- and $\text{D}$--galactopyranose derivatives demonstrate that the configuration of the dioxolane ring influences the conformation of the pyranoid ring in the $\text{D}$-gluco but not in the $\text{D}$-galactopyranose series. The crystal structure of 3,4,6-tri-$\text{O}$-acetyl-1,2-$\text{O}$-(R)--(l-cyano-ethylidene)-α-$\text{D}$-glucopyranose ($\text{1}$) and 3,4,6-tri-$\text{O}$-acetyl-1,2-$\text{O}$-($\text{R}$)-(1-cyano-ethylidene)-α-$\text{D}$-galactopyranose ($\text{2}$)have been determined by X-ray analysis. Lattice parameters for $\text{1}$ are a=20.6021 (11), b=8.0438 (2), c=5.5541 (1) Å and β= 95.588 (3)° for a cell with P21 symmetry. These parameters for $\text{2}$ are a=20.3361 (7), b=10.0907 (2), c=18.9115 (5) Å, β =112.399 (2)°, C2, with two crystallographycally independent molecules. The conformation of the pyranoid ring in both compounds can be described as flattened ⁴C₁ and that of the dioxolane ring as distorted E₁. The importance of the torsion angles for describing problems of configuration is remarked and the use of relative configurational angles is stressed. The ¹H N.M.R. spectra of $\text{1}$ and $\text{2}$ and 3,4,6-tri-$\text{O}$-acetyl-1,2-O-(S)- and (R)-ethylidene-α-$\text{D}$-glucopyranose ($\text{5}$ and $\text{7}$), 3,4,6-tri-O-acetyl--1,2-O-(S)- and ($\text{R}$)-ethylidene-α-$\text{D}$-galactopyranose ($\text{6}$ and $\text{8}$), and 3,4,6-tri-$\text{O}$-acetyl-1,2-$\text{O}$-($\text{S}$)-and ($\text{R}$)-benzylidene-α-$\text{D}$-glucopyranose ($\text{9}$ and $\text{10}$) have been analyzed by using iterative computer methods and N.O.E. measurements. The results indicate that the major solution conformation of the pyranoid ring of the derivatives in the $\text{D}$-gluco series $\text{1}$, $\text{5}$ and $\text{9}$ may be described as flattened ⁴C₁ and that of $\text{7}$ and $\text{10}$ as ²$\text{S}$₅. The major solution conformation of the pyranoid ring in all compounds in the $\text{D}$-galacto series ($\text{2}$,$\text{4}$,$\text{6}$,$\text{8}$) may be described as flattened ⁴$\text{C}$₁.     

Vicinal diester dianions. Annelation with ω-bromoesters. A simple preparation of bicyclo[4.4.0] decan-2-one derivatives valuable in sesquiterpene synthesis.

The dianion of dimethyl, cyclohex-4-ene-1,2-dicarboxylate ($\text{1}$) can be annelated with ethyl 4-bromobutyrate ($\text{2}$) to give cis-dimethyl 1,2,3,5-tetrahydro-1-oxo-4a(4H), 8a (8H)-naphthalenedicarboxylate ($\text{5}$), which is readily transformed into $\text{8a}$, a synthetic intermediate for a number of sesquiterpene syntheses.     

The unexpected thermal instability of 3,4-tetramethylene-1,2-dioxetane as compared to that of cis-3,4-diethyl-1,2-dioxetane.

3,4-Tetramethylene- and $\text{cis}$-3,4-diethyl-1,2-dioxetane ($\text{1}$ and $\text{2}$) were prepared and characterized (for $\text{1}$ - Ea = 22.5 kcal/mole, log A = 12.8; for $\text{2}$ - Ea = 24.5 kcal/mole, log A = 13.1).     

Organophosphorus chemistry. Part 18. Possible intervention of a phospha-alkene in the reactions of a fluoroalkylphosphine with alkoxides

Thermal reactions of phenylphosphine with tetrafluoroethylene and 1,1-difluoroethylene give, respectively, a mixture of phenyl-1,1,2,2-tetrafluoroethylphosphine and 1,2-bis-(phenylphosphino)tetrafluoroethane, and phenyl-2,2-difluoroethylphosphine. The phenyltetrafluoroethylphosphine reacts with an excess of ethanolic or methanolic alkoxide to give the corresponding alkyl phenyl-($\text{E}$)-1-fluoro-2-alkoxyvinylphosphinite and minor amounts of the isomeric alkyl phenyl-($\text{Z}$)-2-fluoro-2-alkoxyvinylphosphinite. The use of an equimolar proportion of sodium methoxide enables the intermediate products methyl phenyl-1,2,2-trifluoroethylphosphinite and methyl phenyl-($\text{E}$)-1,2-difluorovinylphosphinite to be isolated: further reaction of these with methoxide yields the corresponding ($\text{E}$)-1-fluoro-2-methoxyvinylphosphinite. The reactions are discussed in terms of mechanisms which involve either an intermediate phospha-alkene or a hydride ion shift.     

Zur deprotonierung von chloromethyleniminiumchloriden

Deprotonation of chloromethyleniminium chlorides ($\text{1}$, $\text{13}$) leads to cis-trans-isomeres 1,2-diamino-1,2-dichloro-ethenes ($\text{3a}$, $\text{3b}$ resp. $\text{14a}$, $\text{14b}$); their reactivity is described.     

Synthesis and physical properties of 6,12-diarylazuleno[1,2-b]azulenes

The structure of a minor dimer ($\text{2a}$) of 1-arylcycloheptatrienylidenethylene was determined by X-ray crystallography. Dehydration of $\text{2a}$ and $\text{2b}$ gave novel non-benzenoid aromatics---6,12-diarylazuleno[1,2-b]azulenes ($\text{3a}$ and $\text{3b}$), whose electronic and NMR spectral properties were reported.     

Synthesis of oxazolidin-2-ones using carbonate ion on a polymeric support

Through the insertion of a carbon dioxide molecule, the oxazolidin-2-ones ($\text{5a}$) and ($\text{5b}$) were prepared by treataent of the salts ($\text{4a}$) and ($\text{4b}$) with carbonate anion on polymeric support. The hydrolysis under basic conditions of ($\text{5a}$) and ($\text{5b}$) afforded the erythro-3-amino-1,2-diols ($\text{6a}$) and ($\text{6b}$) which were fully acetylated: the 2-amino-2-deoxyerythritol derivative ($\text{7b}$) was obtained in 91% yield.     

Spiroadamantyl stabilization of sulfur-substituted 1,2-dioxetanes

With the help of spiroadamantyl substitution, the first sulfur-substituted 1,2-dioxetanes $\text{9}$ and $\text{10}$, respectively derived from thiophenylmethyleneadamantane ($\text{7}$) and 2-adamntylidene-1, 3-dithian ($\text{8}$) were prepared via singlet oxygenation and detected by NMR.     

Dinuclear iron carbonyl complexes of 3H-1,2-diazepines

3H-1,2-Diazepines ($\text{1}\text{2}$) give dinuclear complexes ($\text{3}\text{4}$) on reaction with diiron nonacarbonyl. Complexation much reduces the rate of the [1,5] sigmatropic hydrogen shift across the diazepine ring and also reduces the activation energy for ring inversion.     

5,12-dihydro-6,11-didehydronaphthacene,A derivative of 1,4-didehydronaphthalene

Treatment of the di-lithium derivative of 1,2-diethynyl-benzene ($\text{1}$) with $\text{o}$-xylene-α,α′-diol di-$\text{p}$-toluenesulphonate ($\text{2}$) in tetrahydrofuran led to 5,12-dihydronapthacene ($\text{5}$) as the only identifiable product. This reaction presumably involves 5,12-dihydro-6,11-didehydronaphthacene ($\text{4}$) as an intermediate, and this was confirmed by the formation of 5,12-dihydro-6,11-dideuterio-naphthacene when the reaction was carried out in tetrahydrofuran-$\text{d}$₈.     

Addition of boron enolates to isoquinolinium salts: A facile synthesis of 1-β-keto substituted 2-ethoxycarbonyl-1,2-dihydroisoquinolines and their cyclization

An efficient method to synthesize 1-β-keto substituted 2-ethoxycarbonyl (or 2-acetyl)-1,2-dihydroisoquinolines ($\text{3}$) is described, utilizing boron enolates and isoquinolinium salts. The products were treated with sodium ethoxide to afford the corresponding cyclic compounds ($\text{6}$).     

Alicyclische verbindungen-v. darstellung diverser 1,3-butadienylcyclobutane

$\text{cis}$-($\text{3}$) and $\text{trans}$-1,3-Butadienylcyclobutane ($\text{4}$), all-$\text{trans}$-1-(1 ,3-butadieny1 )-2- vinylcyclobutane ($\text{10}$), and all-$\text{trans}$-1,2-bis(1,3-butadienyl)cyclobutane ($\text{15}$) have been prepared from readily available starting materials, and pyrolyzed to various cyclohexenes.