Planarisierung von tetrakoordiniertem Kohlenstoffatom. Synthese des überbrückten all-cis-[5.5.5.5]Fenestrans 13-Oxapentacyclo[5.5.2.11.7.04,15.010,15] pentadecan-14-on

Planarisation of Tetracoordinate Carbon Atom, Synthesis of the Brigded all-cis-[5.5.5.5]Fenestrane 13-Oxapentacyclo[5.5.2.1^1,7.0^4,15.0^10,15]pentadecan-14-one The synthesis of the ketolactone 23 from (Z,Z)-1,5-cyclooctadiene is reported. Transannular carben insertion, achieved via photolysis of the deprotonated (2,4,6-trisisopropylphenylsulfonyl)hydrazone of 23 gives the bridged all-cis-[5.5.5.5]fenestrane 3 .     

General approach for the synthesis of polyquinanes: stereospecific,regiospecific entry into the tetracyclo-[6.6.0.01,5.08,12]tetradecane system

The synthesis of tetracyclo-[6.6.0.0^1,5.0^8,12]tetradecane-4,6,11,13-tetraone $\text{12}$ is described.     

General approach for the synthesis of polyquinenes via the weiss reaction. Preparation of the chiral tetracyclo [6.6.0.01,5.08,12]tetradecane-3,6,10,13,-tetraene

The aldol approach to construct the tetracyclic polyquinane skeleton of $\text{12}$, followed by hydroboration and the HMPA mediated dehydration of four hydroxyl groups has resulted in the facile synthesis of the chiral polyquinene, tetracyclo[6.6.0.0^1,5.0^8,12]-tetradecane-3,6,10,13-tetraene $\text{2}$. This method completely avoids the troublesome fragmentation reactions earlier encountered when the strained tetraone $\text{9}$ was reacted with nucleophilic reagents.     

Asymmetric total synthesis of stoechospermol using intramolecular (2+2) photocycloaddition reaction

The first asymmetric total synthesis of stoechospermol, a representative spatane diterpene having $\text{cis}$, $\text{anti}$, $\text{cis}$-tricyclo[5.3.0.0^2,6]decane ring system, was achieved. Using the intramolecular asymmetric (2+2) photocycloaddition reaction of the diastereomeric ester 11, the readily available butenolide 9 was transformed into the optically active dilactone 12a and 12b. Subsequent construction of tricyclic carbon ring system and introduction of substituents in a right stereochemistry gave rise to optically pure stoechospermol 1.     

Zwei neue pentacyclische dimere des cycloheptatriens

Titanium - catalyzed dimerization of cycloheptatriene affords pentacyclo[7.5.0.0^2,8.0^5,14.0^7,11]tetradeca-3,12-diene, $\text{3}$, and pentacyclo[8.4.0.0^3,7.0^4,14.0^6,11]tetradeca-8,12-diene, $\text{4}$. By heating, $\text{3}$ is converted quantitatively into $\text{4}$.     

[2+2] Cycloaddition of benzyne to cis,trans- and cis,cis-1,5-cyclooctadiene

The relative rates of formation of $\text{cis}$ and $\text{trans}$ [2+2]cycloadducts of benzyne to $\text{cis}$, $\text{trans}$- and $\text{cis}$, $\text{cis}$-1,5-cyclooctadiene, $\text{trans}$- and $\text{cis}$-cyclooctene are discussed and properties of the adducts (e.g., their unusual hydrogenation) are described.     

Synthesis of (4.5.5.5]fenestrane and a [4.4.5.5]fenestrane derivative

The synthesis of tetracyclo[5.4.1.0^4,12.0^9.12]dodecan-6-one $\text{12}$ via an intramolelecular photocycloaddition, its reduction to the hydrocarbon $\text{13}$ and its ring-contraction to tetracyclo-[4.4.1.0^3,11.0^9,11]undecane derivative $\text{16}$ is described.     

Concerning the “novel intramolecular hydrogen bond to a trans-syn,s-cis formazan system”: solution isomers of 3-carboxymethylthio- and 3-methoxy-carbonyl-1,5-diphenylformazan

Spectroscopic studies of the [1,5-¹⁵N₂]-labelled title compounds demonstrate the presence of the yellow trans-anti,s-trans ($\text{1}$) and the red trans-syn,s-cis ($\text{2}$) isomers in solution. There is no experimental evidence supporting the postulated novel hydrogen bridge $\text{5}$.     

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.     

Bridgehead nitrogen heterocycles from 2,4,6-triphenyl- pyrylium cation and thiosemicarbazide or thiocarbohydrazide

2,4,6-Triphenylpyrylium with thiosemicarbazide and thiocarbohydrazide, gives 2-pyrazolines $\text{3a}$ and $\text{3b}$ which undergo cyclization yielding pyrazolo(1,5-c]pyrimidine 5 and pyrazolo [2,3-d]-1,2,4-triazepine $\text{7}$ derivatives, respectively. Reaction of $\text{7}$ with phenacyl bromides gave 1,3-thiazolo[3,2-b]pyrazolo [2,3-d]-1,2,4-triazepin-4-iums $\text{10}$. Compound $\text{3a}$ on treatment with phenacyl bromides gave 1-(4'-aryl-thiazol-2'-yl)-2-pyrazoline derivatives $\text{6}$. Compound $\text{3b}$ reacts with acyl chlorides to give pyrazolo[1,5-c]pyrimidine derivatives $\text{14}$, and with aromatic aldehydes giving the 2-(Δ^2'1 pyrazolin-1-yl)-5-aryl-1,3,4-Δ²-thiadiazolines $\text{12}$ which were easily converted to the corresponding 2-(Δ²-pyrazolin-1-yl)-5-aryl-1,3,4-thiadiazoles $\text{13}$.     

Potential metabolites of carcinogenic aza aromatic hydrocarbons synthesis of K-region oxide,phenol and dihydrodiols of 7-methylbenz[c]acridine

The potential K-region metabolites, $\text{trans}$- and $\text{cis}$-5,6-dihydroxy-7-methyl-5,6-dihydrobenz[c]acridine, 5,6-epoxy-7-methyl-5,6-dihydrobenz[c]acridine and 5-hydroxy-7-methylbenz[c]acridine, of 7-methylbenz[c]acridine have been synthesised.     

Intramolecular diels-alder reactions of dienamines with acrylates: trends in stereoselectivity upon substitution.

Intramolecular Diels-Alder reactions of all-$\text{trans}$ ethyl 10-diethylamino-2,7,9-decatrienoate and 11-diethylamino-2,8,10-trienoate occur readily to produce $\text{trans}$ and $\text{cis}$-fused products in ratios of 85:15 and 55:45, respectively.     

The nature of the excited states in all-trans-retinal Schiff bases

The temperature dependent CD spectra of two chiral Schiff bases of all-$\text{trans}$-retinal reveal a three-band absorption pattern for the retinal chromophor. A preliminary analysis suggests that the band at 260 nm corresponds to the $\text{cis}$-peak.     

Synthesis of a tetracyclodecenone with two orthogonal π-electron systems via a 1,3-through cage elimination in a bridgehead substituted 1,3-bishomocubyl acetate

Stereoselective reduction of 1,3-bishomocubanone acetate $\text{1}$ followed by mesylation leads to an epimeric mixture of mesylates $\text{3}$. Base induced homoketonization of the anti-epimer $\text{3b}$ affords tetracyclo[5.3.0.0^2,5 O^4,8]decenone $\text{4}$.     

Exo/emdo soltolysis rate ratios in constrained 2-norbornyl systems

Tetracyclol[6.2.1.0^2,6.0^5,10]undec-3-yl derivatives ($\text{6}$ - $\text{8}$) show typically high tertiary exo/endo solvolysis rate ratios, but the ratios for secondary reactants are suppressed. The rate and product data support the theory of anchimeric assistance in the parent $\text{exo}$-2-norbornyl solvolysis.     

Olefin metathesis in polycyclic frames 1. A new way to cis, syn, cis - tricyclopentanoids (acs-C11-triquinanes)

A novel olefin metathesis sequence permits ready access to functionalised $\text{cis}$, $\text{syn}$, $\text{cis}$-tricyclo [6.3.0.0^2,6] undecane based bis-enones. These bis-enones have been shown to undergo cage cyclisation in sunlight with remarkable ease and efficiency.     

Substituted cyclononatetraenes and nonafulvenes

Reaction of $\text{cis}$,$\text{cis}$,$\text{cis}$,$\text{cis}$-[9]annulene anion ($\text{1}$) with electrophiles ($\text{2a}$-$\text{d}$) leads to substituted $\text{cis}$,$\text{cis}$,$\text{cis}$,$\text{cis}$-1,3,5,7-cyclononatetraenes ($\text{3a}$-$\text{d}$) which are precursors for the preparation of 10- and 10,10′-donor-substituted nonafulvenes (e.g. $\text{7b′}$$\text{e′}$). The influence of solvent and temperature on the ¹H-nmr spectra of the nonafulvenes $\text{7b′}$-$\text{h′}$ has been investigated.     

Nargenicin model studiess: dehydrative rearrangement of a dihydroxyoctahydronaphthalene

Cyclic ether formation by dehydration of a cis-fused 5-acetyl-1,5-dihydroxyoctahydronaphthalene occurs with rearrangement to give a 12-oxatricyclo[5.4.1^1,7.O^3,8]dodecene rather than the 11-oxatricyclo[4.4.1^1,6.O^2,7]undecene system of the nargenicin antibiotics.     

Coordination chemistry of higher oxidation states. 10 [1]. Oxofluoroanions of osmium(VIII) [OsO4F2]2− and [OsO3F3]−

Trioxotrifluoroosmates(VIII) M[OsO₃F₃] (M = Cs, Rb, K) have been prepared by direct combination of OsO₃F₂ and the appropriate alkali fluoride MF. The reaction of OsO₄ with M′F (M′ = Cs, Rb) in aqueous solution produces the tetraoxodifluoroosmates(VIII) M′₂[OsO₄F₂]. On the basis of their vibrational spectra the assignment of a $\text{fac}$ (C_3v) structure to [OsO₃F₃]^? and a $\text{cis}$ (C_2v) to [OsO₄F₂]^2? is proposed. The electronic spectra of the anions have been recorded and are interpreted using the optical electronegativity concept.     

Amino-sulphur-fluorine derivatives as fluoride ion donors: preparation of three- and four-coordinated cations of sulphur (IV) and (VI) [1,2]

Pentacoordinated aminosulphur (IV) trifluorides, R₂N$\text{S}$F₃, (in this paper the lone pair in S(IV)-derivatives is always considered as a ligand) and aminosulphur(VI)-oxidetrifluorides, R₂NS(O)F₃, readily lose a fluoride ion to Lewis acids (AsF₅, SbF₅, BF₃) to give sulphur-containing cationic species [R₂N$\text{S}$F₂]⁺ and [R₂NS(O)F₂]⁺ with tetracoordinated sulphur. Tetracoordinated neutral dialkylaminosulphur(IV)-oxidefluorides, R₂N$\text{S}$(O)F, and amino-imino sulphur(IV)fluorides, R₂N$\text{S}$(=NR_f)F, give three-coordinated sulphur cations [R₂N$\text{S}$O]⁺] or [R₂N$\text{S}$NR_f]⁺.The three-coordinated sulphur(VI)cation [R₂NS(O)NR]₊ has also been formed.