Study of the inversion of 4-benzamido-3-hydroxythiophane

Inversion during the acid hydrolysis of trans-4-benzamido-3-hydroxythiophane is accomplished through the intermediate formation of cis-2-phenyltetrahydrothieno[3,4-d]oxazoline. The latter has cis ring fusion, and the oxazoline ring is planar. Opening of the oxazoline ring is not accompanied by inversion and leads to cis-3,4-substituted thiophanes. Migration of the acyl group from the nitrogen to the oxygen atom was detected in substituted thiophanes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No.10, pp. 1339–1344, October, 1971.     

Study of the formation of 2-substituted 3a,4,6,6a-tetrahydrothieno[3,4-d]oxazolines from cis- and trans-4-amino-3-hydroxythiophans

The formation of 2-substituted 3a,4,6,6a-tetrahydrothieno[3,4-d]oxazolines from N-acyl-substituted cis-and trans-4-amino-3-hydroxythiophans in deuteroacetic acid and by the action of thionyl chloride was studied. Only the derivatives of cis-4-amino-3-hydroxythiophans are cyclized in deuteroacetic acid. The formation of an oxazoline ring from 4-amino-3-hydroxythiophan by the action of thionyl chloride depends both on the relative position of the hydroxy and amino groups and on the character of the acyl substituent attached to the amino group.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 913–917, July, 1974.     

Hydrolytic metal-mediated coupling of dialkylcyanamides at a Pt(IV) center giving a new family of diimino ligands

Addition of excess R(2)NCN to an aqueous solution of K(2)[PtCl(4)] led to the precipitation of [PtCl(2)(NCNR(2))(2)] (R(2) = Me(2) 1; Et(2) 2; C(5)H(10) 3; C(4)H(8)O, 4) in a cis/trans isomeric ratio which depends on temperature. Pure isomers cis-1-3 and trans-1-3 were separated by column chromatography on SiO(2), while trans-4 was obtained by recrystallization. Complexes cis-1-3 isomerize to trans-1-3 on heating in the solid phase at 110 degrees C; trans-1 has been characterized by X-ray crystallography. Chlorination of the platinum(II) complexes cis-1-3 and trans-1-4 gives the appropriate platinum(IV) complexes [PtCl(4)(NCNR(2))(2)] (cis-5-7 and trans-5-8). The compound cis-6 was also obtained by treatment of [PtCl(4)(NCMe)(2)] with neat Et(2)NCN. The platinum(IV) complex trans-[PtCl(4)(NCNMe(2))(2)] (trans-5) in a mixture of undried Et(2)O and CH(2)Cl(2) undergoes facile hydrolysis to give trans-[PtCl(4)[(H)=C(NMe(2))OH](2)] (9; X-ray structure has been determined). The hydrolysis went to another direction with the cis-[PtCl(4)(NCNR(2))(2)] (cis-5-7) which were converted to the metallacycles [PtCl(4)[NH=C(NR(2))OC(NR(2))=NH]] (11-13) due to the unprecedented hydrolytic coupling of the two adjacent dialkylcyanamide ligands giving a novel (for both coordination and organic chemistry) diimino linkage. Compounds 11-13 and also 14 (R(2) = C(4)H(8)O) were alternatively obtained by the reaction between cis-[PtCl(4)(MeCN)(2)] and neat undried NCNR(2). The structures of complexes 11, 13, and 14 were determined by X-ray single-crystal diffraction. All the platinum compounds were additionally characterized by elemental analyses, FAB mass-spectrometry, and IR and (1)H and (13)C[(1)H] NMR spectroscopies.     

Short, highly efficient syntheses of protected 3-azido- and 4-azidoproline and their precursors

[structure: see text] An improved synthesis of protected cis- and trans-3-azido-L-proline and cis- and trans-4-azido-L- and -D-proline is reported. These compounds have been synthesized from the corresponding hydroxyproline precursors using diphenylphosphoryl azide under Mitsunobu conditions. Short, highly efficient syntheses of these precursors are described, based on a new lactone-opening reaction and p-nitrobenzoate hydrolysis under very mild conditions.     

Reaction of cis- and trans-4-alkoxycarbonylamino-3-hydroxythiophans with thionyl chloride

The reaction of cis- and trans-4-alkoxycarbonylamino-3-hydroxythiophans with thionyl chloride gives chlorosulfites. trans-4-Alkoxycarbonylamino-3-chlorosulfito-thiophans are converted to cis-3a,4,6,6a-tetrahydrothieno[3,4-d]oxazolidone by heating or by treatment with pyridine. cis-4-Carboalkoxyamino-3-hydroxythiophans form 3-carboalkoxy-3a,4,6,6a-tetrahydrothieno[3,4-d]oxathiazolidones.     

Research on 1-azabicyclic compounds

1-(2-Furyl)-3-amino-4,4-dimethylpentane was used to obtain 3-tert-butyl-1,2-dihydropyrrolizine, the catalytic hydrogenation of which over Rh/Al₂O₃ at room temperature gives a mixture of cis- and trans-3,8-H-3-ter-butylpyrrolizidines with predominance of the cis isomer, whereas hydrogenation at 90–100 °C gives a mixture containing the trans isomer as the principal component. The three-dimensional structures of the isomers follow from data on the catalytic hydrogenation and isomerization and the IR, Raman, and PME spectra. A considerable percentage of the trans-fused form is characteristic for cis-3,8-H-3-tert-butylpyrrolizidine.     

Transformation of 4-(1-dimethylaminoethylidene)-2-phenyl-5(4H)-oxazolone into methyl 2-benzoylamino-3-oxobutanoate. The synthesis of 1-substituted 4-benzoylamino-3-methyl-5(2H)-pyrazolones

Methyl 2-benzoylamino-3-oxobutanoate ( 3 ) was prepared from hippuric acid (1) which was converted with N,N-dimethylacetamide and phosphorus oxychloride into 4-(1-dimethylaminoethylidene)-2-phenyl-5(4H)-oxazolone ( 2 ) followed by hydrolysis with hydrochloric acid in methanol. Compound 3 was treated with hydrazines 4 to give 4-benzoylamino-3-methyl-1H-pyrazol-5(2H)-one ( 6a ) and its 1-substituted derivatives 6b-j . The corresponding hydrazones 5f, i, j were isolated as intermediates.     

Fluorocyclohexanes. Part XVI. The six H-trifluoromethyldecafluoro- and two of the 2H,4H-trifluoromethylnonafluoro-cyclohexanes

Fluorination of benzotrifluoride by cobaltic fluoride at 260–280° gave, besides the fluorocarbon, the six possible tridecafluoromethylcyclohexane isomers, and two 2H,4H-dodecafluorides. Of the C₇HF₁₃ compounds, only the cis?2H-, and the cis- and trans-4H-isomers could be isolated pure. The two 3H-isomers were made by pyrolysis of perfluoro(1-methyl-3-isopropylcyclohexane) in the presence of toluene. The trans-2H-isomer was made by further fluorination of one of the 2H,4H-dodecafluorides. Aqueous potash and the cis-2H-tridecafluoride gave 1-trifluoromethylnonafluorocyclohex-1-ene, which with stronger alkali hydrolysed to 1-carboxynonafluorocyclohex-1-ene. The cis- and trans- 2H and 4H-tridecafluorides were dehydrofluorinated by sodium fluoride at 320–380° (the cis-isomer of each pair reacted faster than the trans- : axial versus equatorial hydrogen) to give, respectively, the 1-trifluoromethylnonafluoro-ene and the 4-trifluoromethyl-isomer. The latter was isomerised to the former by sodium fluoride at 500–600°. The 1?CF₃-ene gave hexafluoroglutaric acid on oxidation with alkaline potassium permanganate.     

Bis(acetylacetonato)ruthenium(II) complexes containing alkynyldiphenylphosphines. Formation and redox behaviour of [Ru(acac)2(Ph2PC triple bond CR)2] (R=H, Me, Ph) complexes and the binuclear complex cis-[{Ru(acac)2}2(micro-Ph2PC triple bond CPPh2)}2

Two equivalents of Ph(2)PC triple bond CR (R=H, Me, Ph) react with thf solutions of cis-[Ru(acac)(2)(eta(2)-alkene)(2)] (acac=acetylacetonato; alkene=C(2)H(4), 1; C(8)H(14), 2) at room temperature to yield the orange, air-stable compounds trans-[Ru(acac)(2)(Ph(2)PC triple bond CR)(2)] (R=H, trans-3; Me=trans-4; Ph, trans-5) in isolated yields of 60-98%. In refluxing chlorobenzene, trans-4 and trans-5 are converted into the yellow, air-stable compounds cis-[Ru(acac)(2)(Ph(2)PC triple bond CR)(2)] (R=Me, cis-4; Ph, cis-5), isolated in yields of ca. 65%. From the reaction of two equivalents of Ph(2)PC triple bond CPPh(2) with a thf solution of 2 an almost insoluble orange solid is formed, which is believed to be trans-[Ru(acac)(2)(micro-Ph(2)PC triple bond CPPh(2))](n) (trans-6). In refluxing chlorobenzene, the latter forms the air-stable, yellow, binuclear compound cis-[{Ru(acac)(2)(micro-Ph(2)PC triple bond CPPh(2))}(2)] (cis-6). Electrochemical studies indicate that cis-4 and cis-5 are harder to oxidise by ca. 300 mV than the corresponding trans-isomers and harder to oxidise by 80-120 mV than cis-[Ru(acac)(2)L(2)] (L=PPh(3), PPh(2)Me). Electrochemical studies of cis-6 show two reversible Ru(II/III) oxidation processes separated by 300 mV, the estimated comproportionation constant (K(c)) for the equilibrium cis-6(2+) + cis6 <=> 2(cis-6(+)) being ca. 10(5). However, UV-Vis spectra of cis-6(+) and cis-6(2+), generated electrochemically at -50 degrees C, indicate that cis-6(+) is a Robin-Day Class II mixed-valence system. Addition of one equivalent of AgPF(6) to trans-3 and trans-4 forms the green air-stable complexes trans-3 x PF(6) and trans-4 x PF(6), respectively, almost quantitatively. The structures of trans-4, cis-4, trans-4 x PF(6) and cis-6 have been confirmed by X-ray crystallography.     

Study of the reaction of cis- and trans-4-acylamino-3-hydroxythiophans with thionyl chloride

The reaction of cis- and trans-4-acylamino-3-hydroxythiophans with thionyl chloride was studied. It was found that chlorosulfites are initially formed with retention of the configuration of the starting compound. 2-Substituted 3a,4,6,6a-tetrahydrothieno[3,4-d]oxazoline is formed from trans-4-acylamino-3-chlorosulfitothiophans by thermal reaction or in the presence of pyridine, whereas trans-4-acylamino-3-chlorothiophans are obtained from cis-4-acylamino-3-chlorosulfitothiophans; both reactions proceed with inversion of configuration.     

Room-temperature photochromism in cis- and trans-[Ru(bpy)2(dmso)2]2+

We report on phototriggered Ru-S --> Ru-O and thermal Ru-O --> Ru-S intramolecular linkage isomerizations in cis- and trans-[Ru(bpy)2(dmso)2]2+. The cis complex features only S-bonded sulfoxides (cis-[S,S]), whereas the trans isomer is characterized by S- and O-bonded dmso ligands. Both cis-[S,S] and trans-[S,O] exhibit photochromism at room temperature in dmso solution and ionic liquid (IL). Rates of reaction in IL were monitored by UV-visible spectroscopy and are similar to those reported in dmso solution (k(O-->S) ranges from approximately 10(-3) to 10(-4) s(-1)). Cyclic voltammetric measurements of cis-[S,S] and trans-[S,O] are consistent with an electrochemically triggered linkage isomerism mechanism. While both cis-[S,S] and trans-[S,O] are photochromic at room temperature, neither complex is emissive. However, upon cooling to 77 K, cis-[S,S] exhibits LMCT (ligand-to-metal charge transfer) emission typical of many ruthenium polypyridine complexes. In contrast to cis-[S,S], trans-[S,O] does not show any detectable emission even at 77 K.     

Furan forming reactions of cis-2-alken-4-yn-1-ones

[reactions: see text] The cis-2-alken-4-yn-1-one, 1-phenyl-cis-2-penten-4-yn-1-one (cis-1), readily dimerizes on treatment with weak acid to give the 1,2-difurylethylenes, trans- and cis-1,2 di(2-(5-phenylfuryl))ethene (trans-1 and cis-2), in 62% and 23% yields, respectively. Trimerization of cis-1 to trans,trans-1,2,3-tri(2-(5-phenylfuryl)cyclopropane (4) occurred as a byproduct of treatment with weak acid. These reactions demonstrate the 2-furylcarbenoid reactivity of cis-2-alken-4-yn-1-ones.     

Diversity-oriented synthesis of enantiomerically pure steroidal tetracycles employing Stille/Diels-Alder reaction sequences

Various steroid analogues were synthesized by Stille coupling of bicyclo[4.3.0]nonenylstannanes cis-/trans-8 and 14 with cyclohexenol triflates 17 and 18 and subsequent Diels-Alder reactions of the resulting dienes. The enantiomerically pure bicyclo[4.3.0]nonenylstannanes cis- and trans-8 were prepared in good yields via the enol triflates cis- and trans-7, obtained from the bicyclo[4.3.0]non-2-en-3-one 5. The alkenylstannane 14 was obtained from the [2+2] cycloadduct 10 a produced from addition of dichloroketene to the enantiomerically pure and protected bishydroxycyclohexadiene 9 a (65 %). Treatment of 10 a with diazomethane, reduction of the dichloromethylene group, and trapping with tributyltin chloride after lithium-for-bromine exchange, yielded the bicyclo[4.3.0]nonenylstannane 14 (23 % over four steps). Stille couplings provided the tricyclic dienes cis-/trans-19 in good yields (73-77 %), whereas the tricyclic diene 20 was obtained in only 34 % yield at best. Diels-Alder reactions of trans-19 with various reactive dienophiles yielded the novel steroidal compounds trans-21 to trans-26 with complete diastereoselectivity. Heating the dienes cis-19 or 20 with maleic acid derivatives provided the corresponding tetracycles cis-23alpha,beta and 27alpha,beta with a cis-C,D ring junction, each as mixtures of two diastereomers. Less reactive dienophiles required higher temperatures to promote the relevant cycloaddition with trans-19 to furnish several stereoisomeric forms of trans-28 and trans-29 in significantly lower yields (31-45 %). The selected steroid analogues trans-22 and trans-23 were deprotected in two steps by using acid catalysis to provide trans-31 and trans-33 (91 and 80 % over two steps). Cyclopropanation of trans-30 yielded the cyclopropasteroid analogue 34 (74 %), treatment of which with trifluoroacetic acid furnished the cyclopropasteroid 35 and the 2-methyl-substituted steroid analogue 36 in 40 and 12 % yield, respectively. Aromatic B-ring steroids 38 (69 %) and 39 (5 %) were accessed by dehydrogenation of trans-24 with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone.     

Reversible photoswitchable wettability in noncovalently assembled multilayered films

Reversible and irreversible photoinduced changes in surface wettability were observed in noncovalently assembled multilayered films. The multilayered films studied were fabricated from a self-assembled monolayer (SAM) consisting of 4-(10-mercaptodecyloxy)pyridine-2,6-dicarboxylic acid on gold, Cu(II) ions complexed to the pyridine head group of the SAM, and either cis- (film 1) or trans- (film 2) stilbene-4,4'-dicarboxylic acid complexed to the Cu(II) ions. Irradiation of film 1 at wavelengths corresponding to the absorption band of the cis-stilbene isomer resulted in an irreversible chemical change and an irreversible increase in wettability, as indicated by surface contact angle and grazing incidence IR measurements. However, no evidence for cis-/trans-photoisomerization was observed. Films 3 and 4, similar to films 1 and 2 in that they consist of an underlying SAM, an intermediate layer consisting of Cu(II) ions, and either cis- or trans-stilbene-4,4'-dicarboxylic acid as the capping ligand, were fabricated with a mixed SAM that contained both 4-(10-mercaptodecyloxy)pyridine-2,6-dicarboxylic acid and 4-tert-butylbenzenethiol. Irradiation of these films at wavelengths corresponding to stilbene isomer absorption bands resulted in reversible cis- to trans- (film 3) and trans- to cis- (film 4) photoisomerization and reversible switching of the surface wettability between a low wetting state (cis-stilbene) and a high wetting state (trans-stilbene). The difference in observed behavior between films 1 and 2 and films 3 and 4 is attributed to the greater surface spacing afforded by the mixed monolayer, which allows greater conformational flexibility and lowers the steric barriers to isomerization.     

Stereoselective total synthesis of cis- and trans-3-hydroxypipecolic acid

[reaction: see text] 3-Hydroxypipecolic acid, a nonproteinogenic cyclic alpha-amino acid, is a common structural moiety found in a large number of natural and synthetic compounds of medicinal significance. Utilizing D-serine as a chiral template, the present research describes efficient and straightforward routes to cis- and trans-3-hydroxypipecolic acids in enantiopure form. The key steps in the syntheses involve chelation-controlled addition of a homoallyl Grignard reagent to a protected serinal derivative toward stereoselective formation of the corresponding syn-amino alcohol adduct 3. On the other hand, zinc borohydride-mediated chelation-controlled reduction of a serine-derived alpha-aminoketone precursor leads to the formation of the corresponding anti-amino alcohol adduct 4 with high stereoselectivity. Following an efficient sequence of reactions, the above amino alcohol derivatives were subsequently transformed to the corresponding cis- and trans- title compounds, respectively.     

Relationship between the configurations of 2-phenyltetrahydrothiophenium 1-methylides and their rearrangement products

trans-2-Phenyltetrahydrothiophenium 1-methylide (trans-3), which is generated by fluoride ion-induced desilylation of trans-2-phenyl-1-[(trimethylsilyl)methyl]tetrahydrothiophenium salt (trans-2), gave a mixture of 1,4,5,10a-tetrahydro-3H-2-benzothiocine (4) ([2,3]sigmatropic rearrangement product) and 4-methylsulfanyl-1-phenyl-1-butene (5) (Hofmann elimination product). Ylide trans-3 cannot undergo [2,3]sigmatropic rearrangement because the ylide-carbon is too far from the phenyl group, and trans-3 would instead isomerize to cis-3. In this paper, we discuss the mechanism of the isomerization of trans-3 to cis-3.     

Preparation and chemistry of cis- and trans- F4Te(OH)2

Trans-tetrafluoro-orthotelluric acid (mp. 118°) is formed from orthotelluric acid and aqueous HF. Cis-tetrafluoro-orthotelluric acid (mp. 160°) is the only product of the hydrolysis of pentafluoro-orthotelluric acid. With the above compounds as starting materials the stereochemistry of the hydrolysis of TeF₆ can be followed up closely. Interaction of cis- and trans-F₄Te(OH)₂ with CH₂N₂ leads to cis- and trans-F₄Te(OCH₃)₂ and cis- and trans-CH₃OTeF₂OH. Differences in chemical reactivity of these compounds are presented.     

Asymmetric synthesis of trans-3-amino-4-alkylazetidin-2-ones from chiral N,N-dialkylhydrazones

Enantiopure N,N-dialkylhydrazones 3 smoothly react with N-benzyloxycarbonyl-N-benzyl glycine as an aminoketene precursor to afford trans-3-amino-4-alkylazetidin-2-ones 4 as single diasteromers. As an exception, hydrazone 3f (R = OBn) affords cis-(3R,4R)-4f under modified conditions. N-N Bond cleavage of cycloadducts 4 afforded free azetidinones 5 in high yields. [structure: see text]     

Synthesis of nitrosylruthenium complexes containing 2,2':6',2"-terpyridine by reactions of alkoxo complexes with acids

Nitrosylruthenium complexes containing 2,2':6',2"-terpyridine (terpy) have been synthesized and characterized. The three alkoxo complexes trans-(NO, OCH3), cis-(Cl, OCH3)-[RuCl(OCH3)(NO)(terpy)]PF6 ([2]PF6), trans-(NO, OC2H5), cis-(Cl, OC2H5)-[RuCl(OC2H5)(NO)(terpy)]PF6 ([3]PF6), and [RuCl(OC3H7)(NO)(terpy)]PF6 ([4]PF6) were synthesized by reactions of trans-(Cl, Cl), cis-(NO, Cl)-[RuCl2(NO)(terpy)]PF6 ([1]PF6) with NaOCH3 in CH3OH, C2H5OH, and C3H7OH, respectively. Reactions of [3]PF6 with an acid such as hydrochloric acid and trifluoromethansulforic acid afford nitrosyl complexes in which the alkoxo ligand is substituted. The geometrical isomer of [1]PF6, trans-(NO, Cl), cis-(Cl, Cl)-[RuCl2(NO)(terpy)]PF6 ([5]PF6), was obtained by the reaction of [3]PF6 in a hydrochloric acid solution. Reaction of [3]PF6 with trifluoromethansulforic acid in CH3CN gave trans-(NO, Cl), cis-(CH3CN, Cl)-[RuCl(CH3CN)(NO)(terpy)]2+ ([6]2+) under refluxing conditions. The structures of [3]PF6, [4]PF6.CH3CN, [5]CF3SO3, and [6](PF6)2 were determined by X-ray crystallograpy.     

Si-H and Si-Si activation at Pt: synthesis and reactivity of neutral and cationic silyl complexes

Reactions of [Pt(PEt(3))(3)] (1) with the silanes HSiPh(3), HSiPh(2)Me and HSi(OEt)(3) led to the products of oxidative addition, cis-[Pt(H)(SiPh(3))(PEt(3))(2)] (2), cis-[Pt(H)(SiPh(2)Me)(PEt(3))(2)] (3), cis-[Pt(H){Si(OEt)(3)}(PEt(3))(2)] (cis-4) and trans-[Pt(H){Si(OEt)(3)}(PEt(3))(2)] (trans-4). The complexes cis-4 and trans-4 can also be generated by hydrogenolysis of (EtO)(3)SiSi(OEt)(3) in the presence of 1. Furthermore, the silyl compounds cis-4 and trans-4 react with B(C(6)F(5))(3) and CH(3)CN by hydride abstraction to give the cationic silyl complex trans-[Pt{Si(OEt)(3)}(NCCH(3))(PEt(3))(2)][HB(C(6)F(5))(3)] (8). In addition, the reactivity of the complexes cis-4, trans-4 and 8 towards alkenes and CO was studied using NMR experiments.