12-S-CIS conformationally locked retinoids: Thermal and photochemical interconversions leading to new geometric isomers

For 12-$\text{s}$-$\text{cis}$ locked retinal analogues, thermal equilibria are established between 11-$\text{cis}$, 13-$\text{cis}$-1c and 13-$\text{cis}$-2c and between 9-$\text{cis}$, 11-$\text{cis}$, 13-$\text{cis}$-1d and 9-$\text{cis}$, 13-$\text{cis}$-2d; a photoisomerization occurs to transform 2c to $\text{all}$-$\text{trans}$-2a and 2d to 9-$\text{cis}$-2b     

[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.     

Stereospecific synthesis of cis-2-alkenylcyclopropane carboxylic acids; A total synthesis of (±)-cis-chrysanthemic acid

A stereospecific route to $\text{cis}$-2,2-dimethyl-3-alkenyl-cyclopropanecarboxylic Acids is illustrated by a total synthesis of (±)-$\text{cis}$-Chrysanthemic Acid (11). The key step consists of an alicyclic Claisen rearrangement of $\text{O}$-silyl enolates derived from appropriately substituted ($\text{Z}$)-4-hexen-6-olides [e.g.(9)].     

Stereoselectivities of benzonitrile oxide cycloadditions to cis disubstituted cyclopentenes and dihydrofurans

Benzonitrile oxide cycloadds preferentially $\text{anti}$ to the substituents of $\text{cis}$-3,5-di-X-cyclopentenes, where X = OMe, OAc, OCOPh, Br, Cl, and OH. Higher stereoselectivities are found for $\text{cis}$-2,5-di-X-2,5-dihydrofurans. The origins of these selectivities, and contrasts with acyclic and cyclobutene analogs, are described.     

The effect of alkene configuration on the partitioning between the carbenic reactions and the 1,7-electrocyclisation of α-)o-alkenylaryl)diazoalkanes

The 1,7-electroclyclisation of α-($\text{o}$-alkenylaryl)diazoalkenes to 1$\text{H}$-2,3-benzodiazepines is blocked by the $\text{cis}$ substituent in $\text{Z}$ alkenyl groups and the diazo-compounds then react via alternative routes including a new intramolecular carbene reaction to give naphtho[a]cycloheptenes.     

cis Δ5-octahydro-1-naphtalenones and cis Δ5-decahydro-1-naphthalenes (cis-1-decalones) by stereoselective intramolecular diels-alder reaction.

Intramolecular DIELS-ALDER reactions of requisite trienes led to $\text{cis}$-1-decalones, $\text{via}$ an endo intermediate state.     

Synthesis of 4-substituted cis,cis-1,6-cyclodecadienes via cycloalkylation

Cycloalkylation of dimethyl malonate and tosylmethylisocyanide with $\text{cis}$,$\text{cis}$-1,9-dibromonona-2,7-diene has demonstrated the feasibility of direct cyclization as a route to functionalized $\text{cis}$,$\text{cis}$-1,6-cyclodecadienes.     

Direct determination of the configuration of a benzenediazotate: The crystal structure of sy2-sodium benzenediazotate-4-sulphonate

The crystal structure of $\text{syn}$-sodium benzenediazotate-4-sulphonate shows this to be the $\text{cis}$- and not the $\text{trans}$-isomer     

Bis(tricarbonyliron) complexes of P-quinodimethanes: fragmentation and isomerisation under electron impact

EI mass spectra of $\text{trans}$-η⁴,η⁴-[3,6-bis(methylene)-1,4-cyclohexadiene]-bis=(tricarbonyliron) complexes $\text{1a}$, $\text{b}$ are reported. The fragmentation pathway is rationalized by assuming a rearrangement of the $\text{trans}$-bis(tricarbonyliron) complexes into the $\text{cis}$-isomers under electron impact.     

Stereochemical studies—76 saturated heterocycles—63 : synthesis of cis- and trans-n-methyl- and n-benzyl-4.5- and 5,6-tetramethylenetetrahydro-1,3-oxazines; an x-ray study of n-benzyl-cis-4,5-tetramethylenetetrahydro-1,-3-oxazinium- picrate

- The corresponding $\text{cis}$- and $\text{trans-N}$-methyl- and $\text{N}$-benzyl-5,6- and 4,5-tetramethylenetetrahydro-l,3-oxazines $\text{(5a,b-8a,b)}$were synthesized from $\text{cis}$- and $\text{trans-N}$-methyl and$\text{N}$-benzyl-2- aminomethyl-1-cyclohexanols $\text{1a,b,2a,b}$, from $\text{cis}$- and $\text{trans-N}$-methyl- and $\text{N}$benzyl -2-hydroxymethyl-1-cyclohexylamines$\text{(3a,b,4a,b)}$ by reaction with formaldehyde. The aminoalcohols $\text{1a,2a,3a,b}$and $\text{4a,b}$ were prepared in considerably higher yields than in earlier procedures. NMR spectroscopy showed that the $\text{cis}$ isomers of the synthesized oxazines were conformationally homogeneous in solution, and their preferred conformation (inside or outside) depended on the steric requirement of the groups attached to the anellation points, whereas a bulky C-2 substituent had no influence on the predominant conformation. The structure of $\text{N}$-benzyl-$\text{cis}$-4,5-tetramethylenetetrahydro-1,3-oxaziniumpicrate $\text{(7b)}$. determined by X-ray diffraction analysis, was in agreement with the predominant N-outside conformation of the corresponding base, established by means of NMR spectroscopy.     

Electronic spectra of 12-S-CIS conformationally locked retinals

The electronic absorption spectra of the four new 12-$\text{s}$-$\text{cis}$-locked retinals (1a–1d) bearing 7-$\text{trans}$, 11-$\text{trans}$ double bond geometries are described and compared with those of analogous 7-$\text{trans}$, 11-$\text{cis}$-geometries (1e–1h) and parent retinals (2a-h).     

β-tributylstannylacrylates. Stereospecific synthesis via conjugate additon of tributylstaknylcopper

The synthesis of $\text{cis}$- and $\text{trans}$-8-tributylstannylacrylates from conjugate addition of tributylstannylcopper to various β-substituted acrylates is shown to be a highly stereospecific reaction. Of four tributylstannylmetal reagents examined for this conversion, optimum results were obtained with tributylstannylcopper.     

Biogenetic-type synthesis of (±)-dictyopterene A,an odoriferous substance obtained from brown seaweeds, Dictyopteris

Biogenetic-type synthesis of (±)-dictyopterene A ($\text{1}$) was achieved employing 1,$\text{cis}$-5-undecadien-3-ol ($\text{2}$) postulated to be a biosynthetic intermediate of $\text{1}$: this synthesis means that transformation of dictyoprolene ($\text{4}$) into dictyopterene A ($\text{1}$) was formally made.     

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).     

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.     

Synthesis of the 7-cis isomer of the natural leukotriene d4

Methyl 5(S), 6(S)-oxido-11-oxo-7-cis-9-trans-undecadienoate $\text{5}$ was prepared and used for the synthesis of the novel 7-cis-LTD₄ ($\text{9}$) as well as, after isomerization to the all-trans dienal ester $\text{3}$, for that of the natural leukotrienes.     

Synthesis of perfluorochemicals for use as blood substitutes,Part I. Electrochemical fluorination of N-methyldecahydroquinoline and N-methyldecahydroisoquinoline

Electrochemical fluorination of N-methyldecahydroquinoline afforded mainly a mixture of $\text{cis}$ and $\text{trans}$ N-(F-methyl)-F-decahydroquinoline, their rearranged isomers and F-propyl-F-cyclohexane arising from the cleavage at carbon-nitrogen bonds, in a ratio of approximately 2:4:6:3. N-Methyldecahydroisoquinoline was also fluorinated electrochemically to give a mixture of $\text{cis}$ and $\text{trans}$ N-(F-methyl)-F-decahydroisoquinoline, their rearranged isomers and 1-(F-ethyl)-2-(F-methyl)-F-cyclohexane in a ratio of approximately 4:4:6:1. No correlation was found between the $\text{cis}$ and $\text{trans}$ ratio of starting materials and that of the corresponding perfluorinated amines. Fluorination of N-methyl-1,2,3,4-tetrahydroquinoline gave much lower yields.     

Synthesis applications of aza-cope rearrangements. Stereoselective synthesis of trans-alkyl-cis-3a-aryloctahydroindolones.

The reaction of both $\text{cis}$- and $\text{trans}$-2-amino-1-(1-phenylvinyl)- cyclopentanols with aldehydes affords $\text{trans}$-2-alkyl-$\text{cis}$-3a-aryl-4-oxo-octahydro indoles stereoselectively.     

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.     

Formation of 1,2,4-dioxazolidines by electron-transfer photooxygenation of aziridines

DCA-sensitized photooxygenation of $\text{cis}$- and $\text{trans}$-2,3-diphenylaziridine in acetonitrile yields exclusively $\text{cis}$-3,5-diphenyl-1,2,4-dioxazolidine. Photooxygenation of N-alkyl- substituted 2,3-diphenylaziridines provides both isomers of the peroxide. The $\text{cis}$$\text{trans}$ ratio of isomers decreases with increasing size of the group on nitrogen. These stereochemical results provide support for a proposed mechanism involving addition of singlet oxygen to intermediate azomethine ylides.