Stereospecific formation of amidines by 1,1-addition of amines to isocyanides

Addition of secondary amines to isonitriles in the presence of AgCl at low temperature gives isolable but thermodynamically unstable Z-amidines; only the more stable $\text{6E}$ undergoes ring expansion to the imidazoline $\text{7}$.     

Stereochemistry of the reactions of β-halothioethers with NaCN and AgCN

The S_N reactions of NaCN and AgCN with $\text{erythro}$ and $\text{threo}$-2-methylthio-3-halobutanes are reported. The stereochemistry of the resulting nitriles and isonitriles demonstrates that total retention in configuration has taken place in these processes. This disagrees with the accepted explanation for the regioselectivity of these reactions.     

Syntheses of bis(imino)thietans

The reactions of sulfonyliminothiirans ($\text{1}$) with isonitriles and those of ketenimines with arylsulfonyl isothiocyanates yield the title compounds $\text{2}$. In contrast, benzoyl isothiocyanate undergoes a Diels-Alder reaction with ketenimines to give 1,3,5-oxadiazine-4-thiones ($\text{3}$).     

Sterically crowded cyclohexanes-2 synthesis,structure and dynamics of hexaspiro[2.0.3.0.2.0.3.0.2.0.3.0]heneicosane

The synthesis, structure and dynamics of hexaspiro[2.0.3.0.2.0.3.0.- 2.0.3.0]heneicosane $\text{3}$ are described. $\text{3}$ adopts a chair conformation in the crystal state but prefers a chair-to-twistboat equilibrium in solution. The activation parameters of the chair-to-chair interconversion of $\text{3}$ and the closely related hexaspiro[2.0.2.0.2.0.2.0.2.0.2.0]- octadecane ([6]rotane) $\text{4}$ have been determined by DNMR. Some consequences appertaining to the conformation and dynamics of other fully (cyclo-)alkylated cyclohexanes are discussed.     

Alkaline hydrolysis of 2-(trifluoromethyl)imidazo[4,5-f] and -[4,5-h]quinolines

2-(Trifluoromethyl)imidazo[4,5-$\text{f}$] and -[4,5-$\text{h}$]quinoline have been prepared from 5(6),acetamido-2-(trifluoromethyl)benzimidazole and 7,8-diaminoquinoline respectively. These (trifluoromethyl)- quinolines like 2-(trifluoromethyl)imidazoles but unlike 2-(trifluoromethyl) benzimidazoles, undergo hydrolysis in dilute sodium hydroxide to give ultimately the corresponding imidazo[4,5-$\text{f}$] and -[4,5-$\text{h}$]- quinoline, respectively.     

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.     

[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.     

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     

Synthesis and molecular structure of piplartine (=piperlongumine)

The structure of piplartine (=piperlongumine) was established as ($\text{1}$)-$\text{3}$-3',4',5'-trimethoxycinnamoyl-5,6-dihydro-2(1H)-pyridone ($\text{13}$) by synthesis and by an X-ray crystallographic analysis. Model condensation of ($\text{E}$)-3,4,5-trimethoxycinnamoyl chloride and crotonamide gave not the expected cinnamoylcrotonamide, but ($\text{1}$)-$\text{N}$-3', 4', 5' -trimethoxycinnamoyl-3-chlorobutyramide ($\text{12}$).     

Synthesis and characterization of 4-dimethylamino-N-triphenylmethylpyridinium chloride,a postulated intermediate in the tritylation of alcohols

4-Dimethylamino-$\text{N}$-triphenylmethylpyridinium chloride ($\text{1}$) reacts with primary but not secondary alcohols to produce trityl ethers in good yield; in addition, amines may be selectively $\text{N}$- tritylated witth $\text{1}$ in the presence of alcohols.     

Completely stereoselective synthesis of all four stereoisomeric 1-carbamoyloxy-1,3-alkadienes via anti-diastereoselective homoaldol reaction from aldehydes and a single carbon-three-unit

Lithiation of both ($\text{Z}$)- and ($\text{E}$)-3-trimethylsilyl-2-propenyl $\text{N}$,$\text{N}$-diisopropyl carbamate 2 affords the (2$\text{E}$) -lithium compound 3. Aluminium- or titanium-mediated addition to aldehydes, 4 gives (1$\text{E}$)-(3$\text{R}$*4$\text{S}$*)-enol carbamates 7. A stereospecific Peterson elimination (borontriflouride- or base-mediated) introduces the second double bond either with (3$\text{E}$)- or with (3$\text{Z}$)-configuration. So just by reagent selection for each of the two steps, (1$\text{E}$,3$\text{E}$)-, (1$\text{E}$,3$\text{Z}$)-, (1$\text{Z}$,3$\text{E}$)-, or (1$\text{Z}$,3$\text{Z}$)- dienes 8 - 11, respectively, are prepared with stereoselectivities up to > 99.7%     

Per - bicyclophosphoranylation d'alditols

Reaction of bicyclophosphane $\text{1}$ with glycol $\text{2}$, glycerol $\text{3}$, erythritol $\text{4}$, L(-)arabitol $\text{5}$ and dulcitol $\text{6}$ leads to the corresponding per-alkoxybicyclophosphoranes $\text{2p}$ - $\text{6p}$ which are in tautomeric equilibrium with the phosphates forms $\text{2p}$′ - $\text{6p}$′.The amount of these latters increases regularly from traces to 24%.     

The resolution of racemic 2-alkyl-1-aminocyclopropane-1-carboxylic acids

Practical procedures for the resolution of racemic modification of (1$\text{R}$, 2$\text{S}$)-and (1$\text{S}$, 2$\text{R}$)-1-amino-2-ethylcyclopropane-1-carboxylic acid $\text{1a}$,$\text{b}$,(1$\text{R}$, 2$\text{S}$)- and (1$\text{S}$, 2$\text{R}$)-1-amino-2-methylcyclopropane-1-carboxylic acid $\text{2a}$,$\text{b}$, and (1$\text{R}$, 2$\text{R}$)- and (1$\text{S}$, 2$\text{S}$)-1-amino-2-methylcyclopropane-1-carboxylic acid $\text{3a}$,$\text{b}$ are described; the structures as $\text{1a}$,$\text{2a}$, and $\text{3a}$ were confirmed by X-ray-crystallographic methods.     

Stereochemical studies—971a. Saturated heterocycles—991b : An unusual ring-opening reaction of 2-methylthio-3,1-perhydro-benzoxazines. A comparative study of the 3,1 and 1,3-isomers

In the reactions of 2-thioxo-$\text{cis}$- and $\text{trans}$-3,1-perhydrobenzoxazines ($\text{3}$, $\text{4}$) with methyl iodide the hydrogen iodide formed in the S-methylation process brings about ring-opening and gives iodomethylthiolcarbamates ($\text{7}$, $\text{8}$). Under similar conditions, the thioether salts ($\text{15}$, $\text{16}$) of the structurally isomeric $\text{cis}$- and $\text{trans}$-2-thioxo-1,3-perhydrobenzoxazines, corresponding to the unstable intermediates in the former reactions, are stable. Under more vigorous conditions, the $\text{cis}$ isomer thioether salt $\text{15}$ is transformed into the corresponding $\text{cis}$-and $\text{trans}$-l,3-perhydrobenzoxazin-2-ones ($\text{17}$, $\text{18}$) by ring-opening and subsequent ring-closure, whereas the $\text{trans}$ isomer $\text{16}$ gives only $\text{trans}$-1,3-perhydrobenzoxazin-2-one ($\text{18}$).     

Cell free synthesis of O-succinylbenzoic acid from ISO-chorismic acid,the key reaction in vitamin K2(menaquinone) biosynthesis

An enzyme preparation from E. coli catalyses the formation of osuccinylbenzoic acid ($\text{1}$, OSB, i.e. 4-(2′-carboxyphenyl)-4-oxobutanoic acid) from α-ketoglutaric acid and $\text{iso}$-chorismic acid ($\text{2}$) but not from chorismic acid ($\text{3}$).     

New tetrahydropyrans from a marine sponge

Two new tetrahydropyrans have been isolated from the sponge Haliclona sp. From chemical and spectroscopic evidence they are shown to be (1′$\text{R}$, 2$\text{S}$, 2″$\text{E}$, 5$\text{R}$, 6$\text{R}$)-2-(1′-bromethyl)-2,5-dimethyl-6-(penta-2″,4″-dienyl)-tetrahydropyran and (1′$\text{R}$, 2$\text{S}$, 5$\text{R}$, 6$\text{R}$)-2-(1′-bromoethyl)-2,5-dimethyl-6-(pent-4″-enyl)-tetrahydropyran.     

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.     

Synthesis and structure of stilbene crowns.

Syntheses of $\text{E}$- and $\text{Z}$-[a,e]-dibenzo-7,10,13-trioxacyclotrideca-1,3,5-triene, $\text{1}$ (n=1) and $\text{E}$- and $\text{Z}$-[e,a]-dibenzo-7,10,13,16-tetraoxacyclohexadeca-1,3,5-triene, $\text{1}$ (n=2) are described and the X-ray structure of E-$\text{1}$ (n=1) is reported.     

Synthesis of 4″-carboxylated cannabinoids: Stereospecific processes involving ethylidenemalonic ester

4″-Carboxylated-cannabidiol,-Δ¹-and-Δ^1,6-tetrahydrocannabinols and - cannabinol are synthesised. Condensation between aromatic aldehydes and ethylidenemalonic ester gives a 2$\text{E}$,4$\text{E}$-half ester stereospecifically, a reaction which can be used to make 2$\text{E}$-4$\text{E}$- or 2$\text{Z}$,4$\text{E}$-pentadienoates.     

N-Acylated α-aminonitriles and their conversion into 5-aminooxazole, 5(4h)-oxazolone and 4(5h)-imidazolone derivatives

In contrast with the reaction of α-aminonitriles $\text{1}$a, the corresponding $\text{N}$-acylated α-aminonitriles $\text{1}$b-f and oxalyl chloride do not yield pyrazinone derivatives, but 5-aminooxazoles $\text{9}$-$\text{11}$ or 4(5$\text{H}$)-imidazolones $\text{12}$, the latter being converted in some cases into imidazo [2,1-$\text{a}$]isoquinoline-2,5,6(3$\text{H}$)-triones. Reactions of compounds $\text{1}$b-f and ethyl chlorooxoacetate provide evidence for a 5(4$\text{H}$)-iminooxazole intermediate $\text{7}$, which aromatizes to yield 5-aminooxazoles $\text{9}$-$\text{11}$; however, unaromatizable īntermediates of type $\text{7}$ - isolable as 5(4$\text{H}$)y-oxazolones $\text{13}$ after hydrolysis - undergo a catalyzed Dimroth-type rearrangement to give imidazolone derivatives $\text{12}$.