Organometallics in organic synthesis:tricarbonyl-(3-methoxycyclohexa-2,4-dien-1-yl)-iron(1+). A synthetic equivalent of the C-5 cation of cyclohexenone.

Tricarbonyl-(3-methoxycyclohexa-2,4-dien-1-yl)-iron(1+) PF₆(1-) $\text{2}$ reacts with a variety of nucleophiles to give 5-substituted cyclohex-2-enones. $\text{2}$ is shown to be a useful precursor for a convergent synthesis of 5-substituted cyclohex-2-enones and to be synthetically equivalent to the 5-cyclohex-2-enone cation $\text{1}$.     

β-oxa-γ,δ-enones,II. Rearrangement and intramolecular cycloaddition of 1-cyclopentenyloxy-2-propanone.

The title compound $\text{1}$ undergoes an intramolecular photocycloaddition reaction to yield the bis-oxetane $\text{2}$ and a formal 1,3-shift to yield the 1,4-diketone 3. This work reveals a novel aspect of the photochemistry of β-oxa-γ,δ-enones.     

Ciral synthons for the multistriatins

The readily-obtained carbohydrate α-enones $\text{2}$, $\text{5}$ and $\text{8}$ are converted into the four diastereomeric 2,4-di-C-methyl glycopyranosides $\text{4}$$\text{7}$,$\text{10}$,$\text{11}$, which are chiral synthons for the four multistriatins $\text{1a}$-$\text{1d}$.     

Useful synthetic reagents derived from 1-triisopropylsilylpropyne and 1,3bis-[triisopropylsilyl]propyne,direct, stereoselective synthesis of either Z or E enynes

Lithio reagents derived from 1-triisopropylsilylpropyne ($\text{1}$) and 1,3-$\text{bis}$-[triisopropylsilyl]propane ($\text{3}$) are effective for the synthesis of $\text{Z}$ or $\text{E}$ terminal enyne units (CHCHCCH) and for carboncarbon bond formation with halides, aldehydes, ketones, epoxides, and α,β-enones.     

Reactivite des β-cyclopropyl α-enones—I: Etude des transferts electroniques par voltametrie cyclique et de la reduction par l'electron solvate dans l'ammoniac liquide

Species produced by electron transfer to variously substituted bicyclo[3.1.0]hex-3-en-2-ones provide a better insight into the origin of 1,6-addition products sometimes observed by reaction of lithium diorganocuprates with β-cyclopropyl α-enones. Cyclic voltammetry of eight such bicyclohexenones show that the half-lives of the corresponding anion radicals are very short (t_{$\text{1}\text{2}$}?10^?4s) except when the initial molecule is phenyl substituted at C-4. In such cases the anion radicals are very stable (t_{$\text{1}\text{2}$}?6s) owing to the greater charge delocalization and we observe a second wave corresponding to the formation of the Dianion. The reduction of the same substrates by the solvated electron in liquid ammonia exhibits the same difference of behaviour. The molecules giving strongly reactive anion radicals only lead to the straight-forward product expected by conjugate reduction; while the 4-phenyl substituted substrates yield a mixture of products from normal conjugate reduction and rearrangement. This correlation strongly suggest that these last products arise from the rearrangement of the dianion.     

Thermodynamics of metal-ligand bond formation: XVI. Base adducts of some organotin compounds

Thermodynamic data have been obtained by calorimetric titration in benzene solution at 30° for reaction of organotin compounds with Lewis bases; data are reported for forty acid/base systems.Ph₃SnCl forms $\text{1}\text{1}$ adducts of low stability with pyridine (py) or 4-methyl-pyridine (4-mepy). Ph₂SnCl₂, Me₂SnCl₂, Bu₂SnCl₂ and Bu₂Sn(NCS)₂ form simultaneously $\text{1}\text{1}$ and $\text{1}\text{2}$ adducts with py or 4-mepy and $\text{1}\text{1}$ adducts with 2,2′-bipyridine or 1,10-phenanthroline (phen); the enthalpies of formation of the phen adducts are similar to those of $\text{1}\text{2}$ adducts with 4-mepy. With BuSnCl₃ and PhSnCl₃ it was not possible to obtain data for each step in addition of pyridine or 4-mepy. Adduct stabilities increase with increasing chloride substitution and in the order Bu < Me < Ph; adducts of Bu₂Sn(NCS)₂ are more stable than those of Bu₂SnCl₂.Tributylphosphine does not react with Ph₃SnCl but gives $\text{1}\text{1}$ adducts with the other tin compounds; only PhSnCl₃ adds a second molecule of this base. The $\text{1}\text{1}$ adducts are more stable than those with heterocyclic bases. Tributylamine brings about disproportionation of the compounds R₂SnX₂ to R₄Sn and SnX₄NBu₃.     

Reaction of acylaminocyanoesters with 2,4-bis (4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide leading to substituted aminothiazoles. Crysta

2-Acylamino-2-cyanoacetic acid ethyl esters $\text{2a-c}$ react with 2,4-bis (4-methoxyphenyl)-1, 3, 2, 4-dithiadiphosphetane 2,4-disulfide $\text{1}$ in refluxing benzene with formation of 2-alkyl(aryl)-5-aminothiazole-4-carboxylic acid ethyl esters $\text{3a-c}$. Structure $\text{3}$ was established by spectroscopic means and an X ray crystallographic investigation of $\text{3a}$. X-Ray analysis revealed that the thiazole ring, exocyclic nitrogen and carbonyl group forming a hydrogen-bonded cycle are nearly coplanar. A resonance interaction is manifested by distinctly shortened /1.447 (3)/ C_(carbonyl)-C_(thiazole) distance.     

Peri-bridged naphthalenes. 4. chalcogen-bridged acenaphthylenes

Three new electron donors, acenaphtho[5,6-$\text{cd}$]-1,2-dithiole ($\text{1}$), acenaphtho[5,6-$\text{cd}$]-1,2-diselenole ($\text{2}$), and acenaphtho[5,6-$\text{cd}$]-1,2-ditellurole ($\text{3}$), can be prepared in 28%, 22%, and 14% yields respectively by reaction of the elemental chalcogens (S, Se, Te) with 5,6-dilithioacenaphthylene ($\text{4}$). Compound $\text{4}$ is generated by treatment of 5,6-dibromoacenaphthylen ($\text{5}$), for which a convenient preparation is described, with $\text{n}$-butyllithium (2 equiv.) in THF at ?78°C.     

From penicillin to penem and carbapenem. VI1) : Synthesis of dethiathienamycin

A new C₃-unit substitution reaction at C-4 position of 4- acetoxyazetidinone derivative ($\text{1}$ and $\text{5}$) by tetraallyltin ($\text{2}$) in the presence of 1/10 eq. of BF₃-ether in methylene chloride is described. From 4-allylazetidinone derivative ($\text{3}$) via ylid intermediate ($\text{14}$) dethiathienamycin ($\text{16}$) was synthesized.     

Reaktionen an komplexgebundenen Liganden. XXXII.: Synthese und eigenschaften von heteronuklearen mangan-chrom-komplexen mit distickstoff- diazen- und hydrazin-brükenliganden

Synthesis and properties of C₅H₅(CO)₂Mn-N₂H₄-Cr(CC)₅$\text{(1)}$, C₅H₅(CO)₂Mn-N₂H₂-Cr(CO)₅$\text{(2)}$ and C₅H₅(CO)₂Mn-N₂-Cr(CO)₅$\text{(3)}$ are reported. $\text{(1)}$, $\text{(2)}$ and $\text{(3)}$ constitute the first series of heteronuclear complexes in which N₂, N₂H₂ and N₂H₄ are bound to identical metal centers. $\text{(1)}$ and $\text{(3)}$ are obtained by reacting C₅H₅Mn(CO)₂N₂H₄ respectively with Cr(CO)₅THF, $\text{(2)}$ by oxidation of $\text{(1)}$. $\text{(2)}$ disproportionates by addition of base yielding $\text{(3)}$ and H₂. The IR Spectrum of $\text{(2)}$ allows the assignment of five normal vibrations of the diazene ligand; in the IR spectrum of the deuterated analogue all six normal vibrations can be assigned. The ¹H-NMR spectrum of $\text{(2)}$ yields the coupling constant of protons on NN double bonds for the first time; the value of ³J_HH  23,5 Hz points to a trans structure of $\text{(2)}$.     

6-alkyl- and 5,6-dialkyl-2-methoxy-4(3H)-pyrimidinones in the transformations of pyrimidines. Regiospecific 1-N-acylation of pyrimidines.

Transformation of 6- and 5,6-dialkyl-2-methoxy-4(3H)-pyrimidinones (1a and 1b) into 1-$\text{N}$-acylated-pyrimidine derivatives 3($\text{a}$-$\text{f}$) under Friedel-Craft like conditions is presented. In different acylation conditions 4-O-acylated-pyrimidines (5a and 5b) are also obtained. Compounds (3c) and (3f) can be directly converted into 1-$\text{N}$-acyl-protected-isouridine analogues (8a and 8b).     

Investigations on diazo compounds and azides- LXII.: Synthesis and reactions of a-diazo phosphonates with a conjugated 1,3-diene unit

α-Diazo phosphonates with a conjugated 1,3-diene unit are synthesised by the Bamford-Stevens reaction ($\text{2}$ →$\text{4}$→$\text{3}$). They undergo [4+2]-cycloadditions with the dienophile $\text{5}$ to form the tetrahydrotriazolopyridazines $\text{8}$, which possess an unchanged diazo group. In contrast, dimethyl acetylenedicarboxylate ($\text{9}$) reacts exclusively with the diazo dipole of $\text{3}$ to yield the 3H-pyrazoles $\text{10}$, which rearrange to $\text{11}$ by sigmatropic PO-shifts and hydrolyse to form $\text{13}$. The diazo compound $\text{3b}$ isomerises to the pyrazole $\text{16}$ when heated in benzene.     

On cyclopentadienone-ketals and their dimers. A novel rearrangement of α,β-unsaturated ketone dialkyl ketals

The dimers $\text{2a}$ & b) of dimethyl- and diethylcyclopentadienone ketals($\text{1a}$ & b) undergo a novel 1,3-alkoxy-rearrangement to $\text{4}$(a & b). Mild hydrolysis of $\text{2}$ or $\text{3}$ gives the monoketones ($\text{3}$a or b). On strong acid catalysed hydrolysis $\text{2}$, $\text{3}$ or $\text{4}$ afford the cyclopentadienone-dimer($\text{6}$.     

The octant rule. XVI1. COnformation and circular dichroism of syn and anti 2-methylbicyclo[3.1.0]hexan-3-ones,thujone and isothujone

(lS,5S)-exo-2(R)-Methylbicyclo[3.1.0]hexan-3-one ($\text{1}$) and (lS,5S)-endo-2(S)-methylbicyclo[3.1.0]hexan-3-one (2) were synthesized and their circular dichroism (CD) spectra run. Conformational analysis based on molecular mechanics calculations and Karplus equation analyses of vicinal H¦H NMR coupling constants indicate boat-like sofa conformations for both $\text{1}$ and $\text{2}$, with very little ring distortion from the symmetry of the parent bicyclo[3.1.0]hexan-3-one. The lone dissymmetric ψ-axial and ψ-equatorial methyl groups of $\text{1}$ and $\text{2}$, respectively, are both octant consignate. The natural product analogs of $\text{1}$ and $\text{2}$, (?)-3-isothujone ($\text{3}$) and (+)-3-thujone ($\text{4}$) were prepared and examined similarly. Their α-methyl perturbers dominate the CD n-π^★ Cotton effects.     

From penicillin to penem and carbapenem. III C1-unit introduction at C-4 position of azetidinone

Monocyclic β-lactams ($\text{1}$) were converted into 4-cyano derivative $\text{2}$ (C₁-unit introduction) under two phase reaction conditions. The cyano group in $\text{2}$ was successively transformed into $\text{3}$ and $\text{4}$, which are thought to be important precursors for the carbapenem synthesis.     

Heterocyclic polyfluoro-compounds. Part 35 [1] dehydrofluorination of 2,2-bis(trifluoromethyl)- and 2-perfluoroalkyl-3,4-difluoro-oxetans

Solid potassium hydroxide dehydrofluorinates 2,2-bis-(trifluoromethyl)-3,4-difluoro-oxetan to 3-fluoro-4,4-bis-(trifluoromethyl)-2-oxete (59%), 2-pentafluoroethyl-3,4-difluoro-oxetan to 2-tetrafluoroethylidene-3,4-difluoro-oxetan, and $\text{r}$-2-heptafluoro-n-propyl-$\text{t}$-3,$\text{t}$-4-difluoro-oxetan to ($\text{Z}$)-2-hexafluoro-n-propylidene- $\text{cis}$-3,4-difluoro-oxetan. Factors which affect these reactions are discussed.     

Synthesis and intramolecular cyclisation of ortho-hydroxy-2,3,3,3-tetrafluoropropiophenone. Formation of 3-fluoro-4-hydroxycoumarin

Acidic hydrolysis of 1-(o-methoxyphenyl)pentafluoropropene $\text{1}$ gave o-hydroxy-2,3,3,3-tetrafluoropropiophenone $\text{2}$ and o-methoxy-2,3,3,3-tetrafluoropropiophenone $\text{3}$. Compound $\text{2}$ when treated with aqueous potassium hydroxide or methanolic sodium methoxide gave 3-fluoro-4-hydroxycoumarin $\text{4}$. Structure of $\text{4}$ has been established by spectral means and some chemical reactions. The cyclisation mechanism of $\text{2}$ is discussed.     

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.     

Five new steroidal glycosides,pregnedioside-A, -B,and their three monoacetates,from an Okinawan soft coral of Alcyonium sp.

Five new pregnene-type steroidal glycosides, named pregnedioside -a ($\text{1}$), 4′-O-acetyl-pregnedioside-a ($\text{2}$), 3′-O-acetyl-pregnedioside-a ($\text{3}$), pregnedioside-b ($\text{5}$), and 4′-O-acetyl-pregnedioside-b ($\text{6}$), were isolated from an Okinawan soft coral of Alcyonium sp. and their structures were elucidated. These are rare examples of steroidal gylcosides from soft coral.     

The clemmensen reaction of tigogenin. A reinvestigation

The reaction of tigogenin ($\text{1b}$) with amalgamated zinc yields tetrahydrotigogenin ($\text{2b}$) and the furostan $\text{3}$. While $\text{2b}$ undergoes acid catalyzed elimination to give the rearranged product $\text{7}$, $\text{3}$ spontaneously decomposes to a mixture of $\text{4}$ and $\text{5}$.