Substituted propanes: VI. The vibrational spectra and conformations of 1,3-dichloro-, 1,3-bromochloro-, 1,3-dibromo- and 1,3-diiodo-propane

The infrared and Raman spectra of 1,3-dichloro-, 1,3-bromochloro-, 1,3-dibromo- and 1,3-diiodopropane were recorded as liquids and in the crystalline state at low temperatures. Crystals of 1,3-dibromo- and 1,3-diiodopropane formed under ca. 20 kbar pressure at ambient temperature were studied by infrared technique.No evidence was found for the GG₁ conformer (parallel C-halogen bonds), but the other three staggered conformers (GG, AA, and AG) (four for 1,3-bromo-chloropropane) were observed in the liquid. In all the stable low temperature crystals the GG conformers were present, at high pressure 1,3-dibromopropane crystallized in GG and 1,3-diiodopropane in the AA conformation. The C-halogen stretching vibrations have been interpreted in detail. A complete list of fundamentals have been proposed for the GG conformers in each compound, for 1,3-diiodopropane the additional AA fundamentals have been assigned whereas some AG bands were interpreted for each compound.     

Intramolecular 1,3-dipolar cycloaddition of cyclo-1,3-diene-tethered nitrile oxides

Intramolecular 1,3-dipolar cycloaddition of cyclo-1,3-diene- and -1,3,5-triene-tethered nitrile oxides gave tricyclic isoxazolines as a single stereoisomer in most cases. The relative stereochemistry of tricycle-fused isoxazolines resulting from 1,3-dipolar cycloaddition of cyclo-1,3-diene-tethered nitrile oxides is cis-cis, whereas from cyclohepta-1,3,5-triene-tethered nitrile oxides the cis-trans isomer predominates.     

Enzymatic desymmetrization of cis-1,3-cyclohexanedicarboxylic acid diesters

cis-1,3-Cyclohexanedicarboxylic acid (1,3-CHDA) monoesters were prepared in high overall yield and high enantiomeric purity using a three step process from cis/trans-1,3-CHDA. The asymmetry is induced by an enzymatic hydrolytic desymmetrization of a meso cis-1,3-CHDA diester. A judicious choice of ester substituents and enzyme can provide >80% overall yield of either enantiomer in >94% ee.     

Reactions of 1,3-Dialkyl-5-amino-1,3-dihydro-2<Emphasis Type="Italic">H</Emphasis>-imidazo-[4,5-<Emphasis Type="Italic">b</Emphasis>]pyridin-2-ones with acetylacetone and ethyl acetoacetate

1,3-Dialkyl-5-amino-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-ones reacted with acetylacetone to give the corresponding 4-(1,3-dialkyl-2-oxo-1,3-dihydro-2H-imidazo[4,5-b]pyridin-5-ylamino)pent-3-en-2-ones which underwent intramolecular cyclization to 1,3-dialkyl-5,7-dimethyl-1,3-dihydro-2H-imidazo[4,5-b]-[1,8]naphthyridin-2-ones on heating in polyphosphoric acid or diphenyl ether. Analogous reaction of 1,3-dialkyl-5-amino-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-ones with ethyl acetoacetate led to the formation of ethyl 3-(1,3-dialkyl-2-oxo-1,3-dihydro-2H-imidazo[4,5-b]pyridin-5-ylamino)but-2-enoates whose cyclization afforded 1,3-dialkyl-8-hydroxy-7-methyl-1,3-dihydro-2H-imidazo[5,4-b][1,8]naphthyridin-2-ones.     

Synthesis and crystal structure of disiloxane-1,3-diols and disiloxane-1,1,3,3-tetraol

1,3-Dimethyl- or 1,3-divinyl-1,3-di-t-butoxydisiloxane-1,3-diol and 1,3-diphenyldisiloxane-1,1,3,3-tetraol were synthesized by hydrolysis of the corresponding diisocyanatodisiloxanes and tetrachlorodisiloxane. The disiloxanediols were soluble in common organic solvents and thermally very stable, therefore, they could be sublimed without decomposition. X-ray crystallography showed that the disiloxane-1,3-diols in the crystal feature a 1.21 nm diameter columnar array with intermolecular hydrogen bonding. The disiloxane-1,1,3,3-tetraol, on the other hand, revealed molecules with a gauche- and anti-conformation depending on crystallization method which formed a columnar array and a sheet-like array, respectively. It was confirmed that these silanols can be potential building blocks for ladder oligosilsesquioxanes.     

Synthesis of oxoindolin-3-ylidene-1,3-dithioles

An efficient and one-pot synthesis of 2-(2-oxoindolin-3-ylidene)-1,3-dithiole-4,5-dicarboxylates by a three-component condensation reaction of isatins, carbon disulfide and dialkyl acetylendicarboxylates in the presence of Bu₃P is reported. Reaction of carbon disulfide and dialkyl acetylene dicarboxylates with acenaphthylene-1,2-dione, ninhydrine and pyrimidine-tetraone resulted in the formation of 2-(2-oxoacenaphthylen-1(2H)-ylidene)-1,3-dithiole-4,5-dicarboxylates, 2-(1,3-dioxo-1H-inden-2(3H)-ylidene)-1,3-dithiole-4,5-dicarboxylates and 2-(2,4,6-trioxotetrahydropyrimidin-5(6H)-ylidene)-1,3-dithiole-4,5-dicarboxylates, respectively, in the same conditions.     

First regioselective iodocyclization of O-allylselenocarbamates

4-Alkyl-2-imino-1,3-oxaselenolanes were prepared in good yields with high regioselectivity under mild conditions by the reaction of selenocarbamates with I₂ or NIS. The resulting 4-alkyl-2-imino-1,3-oxaselenolanes on dehydrohalogenation gave 4-alkylidene-2-imino-1,3-oxaselenolanes. The formation of the (Z)- or (E)-isomer of 4-alkylidene-2-imino-1,3-oxaselenolanes, strongly depends on the configuration of the double bond of O-allylselenocarbamates.     

Transformations of 1,3-di-p-tolyl-5-p-toluidinomethyl-1,3,5-diazaphosphorinane initiated by electrochemical oxidation at a glassy carbon electrode

Electrochemical oxidation of 1,3-di-p-tolyl-5-p-toluidinomethyl-1,3,5-diazaphosphorinane at a glassy carbon anode yields 5,5′-spirobis(1,3-di-p-tolyl-1,3,5-diazaphosphoniarinane) perchlorate and 1,3-di-p-tolyl-5-p-toluidinomethyl-1,3-diaza-2-carbenia-5-phosphorinane perchlorate. The latter reacts on a Pt^II template to give a complex of a new diphosphine ligand.     

Synthesis of 1,3-bis(N,N-difluoroamino)adamantane: addition of difluoramino radicals to 1,3-dehydroadamantane

1,3-Dehydroadamantane undergoes a facile reaction with tetrafluorohydrazine to give 1,3-bis(N,N-difluoroamino)adamantane, the product of 1,3-NF₂ radical addition.     

Synthesis and characterization of three new thermally stable N-heterocyclic germylenes

Three new stable germylenes, rac-1,3-di-tert-butyl-4,5-dimethyl-1,3-diaza-2-germacyclopentane-2-ylide (1), 1,3-di-tert-butyl-4,4-dimethyl-1,3-diaza-2-germacyclopentane-2-ylide (2), and rac-1,3,4-tri-tert-butyl-1,3-diaza-2-germacyclopentane-2-ylide (3) have been synthesized by the reaction of their corresponding germyl dichlorides with elemental lithium. Full synthetic procedures and characterizations are described.     

Stable carbenes. Synthesis and properties of benzimidazol-2-ylidenes

A new stable crystalline carbene, 1,3-bis(1-adamantyl)benzimidazol-2-ylidene, was synthesized by decomposition of 1,3-bis(1-adamantyl)-2,3-dihydro-1H-benzimidazol-2-ylacetonitrile on heating under reduced pressure. Heteroaromatic 1,3-R₂-disubstituted benzimidazol-2-ylidenes, both stable (R = 1-Ad) and generated in situ (R = Me, Bzl), as well as 1,3,4,5-tetraphenylimidazol-2-ylidene (generated in situ), reacted with acetonitrile to give the corresponding insertion products, 1,3-disubstituted 2-cyanomethyl-2,3-dihidro-1H-(benz)-imidazoles. The geometric parameters of 1,3-bis(1-adamantyl)benzimidazol-2-ylidene, determined by X-ray analysis, suggest its lower aromaticity as compared to imidazol-2-ylidenes and 1,2,4-triazol-5-ylidenes. The structures of 2-cyanomethyl-2,3-dihydro-1H-benzimidazoles, 2-cyanomethyl-1,3,4,5-tetraphenyl-2,3-dihydro-1H-imidazole, and 1-(1-adamantyl)-5-cyanomethyl-3,4-diphenyl-4,5-dihydro-1H-1,2,4-triazole are characterized by partial conjugation in the heteroring; some compounds exhibit luminescence under UV irradiation. 1,3-Bis(1-adamantyl)benzimidazol-2-ylidene reacted with molecular sulfur in benzene to give 1,3-bis-(1-adamantyl)-2,3-dihydro-1H-benzimidazole-2-thione, but it failed to react with selenium under analogous conditions.     

Synthesis of bis-fused tetrathiafulvalene with mono- and dicarboxylic acids

Bis-fused tetrathiafulvalenes with mono- and dicarboxylic acids, 2-{5-(1,3-dithiol-2-ylidene)-[1,3]dithiolo[4,5-d][1,3]dithiol-2-ylidene}-1,3-dithiole-4-carboxylic acid (1) and 2-{5-(1,3-dithiol-2-ylidene)-[1,3]dithiolo[4,5-d][1,3]dithiol-2-ylidene}-1,3-dithiole-4,5-dicarboxylic acid (2) have been synthesized. The electronic structure of 1 and 2 was examined from their optical absorption spectra and using density-functional calculations.     

Selective hydrolysis of anti-1,3-diol-acetonides for the differentiation of 1,3-anti and 1,3-syn diols

A mild and general method for the selective cleavage of anti-1,3-acetonides has been developed for the differentiation of 1,3-anti and 1,3-syn diols in long chain polyolic fragments. The diluted acidic conditions applied to these systems are compatible with other common protecting groups such as silyl ethers and benzyloxymethyl ethers.     

Stereoselective total synthesis of 4-((3S,5R)-3,5-dihydroxynonadecyl)phenol

A stereoselective total synthesis of 4-((3S,5R)-3,5-dihydroxynonadecyl)phenol has been accomplished in two different synthetic approaches. In the first approach, Prins cyclization has been successfully utilized to produce the anti-1,3-diol unit, which was further converted into a required syn-1,3-diol through Mitsunobu reaction. The side chain was constructed through cross metathesis and hydrogenation sequence. In the second approach, the chiral syn-1,3-diol was prepared by a sequence of reactions such as alkylation of 1,3-dithane with (R)-epichlorohydrin, ring opening of the epoxide with vinylmagnesium bromide, and 1,3-syn-reduction of the β-hydroxyketone with NaBH₄ in the presence of diethylmethoxyborane.     

Regiospecific iodocyclization of S-allyl dithiocarbamates: synthesis of 2-imino-1,3-dithiolane and 2-iminium-1,3-dithiolane derivatives

4-Alkyl-2-imino-1,3-dithiolanes and 4-alkyl-2-iminium-1,3-dithiolanes were prepared in excellent yields with complete regiospecificity under mild conditions by the iodocyclization of S-allyl dithiocarbamates. Dehydrohalogenation of the 4-alkyl-2-imino-1,3-dithiolanes gave 4-alkylidene-2-imino-1,3-dithiolanes in excellent yields.     

Heterogeneous photosensitization—IV. The structure and properties of benzaldehyde photopolymer

The basic structure of benzaldehyde photopolymer (BPOL) consists of phenyl groups attached to a carbon-carbon and carbon-oxygen chain. The average BPOL molecule contains 12 monomer units. Relative rates for the BPOL photosensitized dimerization of 1,3-cyclohexadiene and the isomerizations of the 1,3-pentadienes, cis-1,2-dichloroethylene and cis-2-butene are reported. The BPOL photosensitized isomerizations of the 1,3-pentadienes in the visible (λ > 395 nm) proceed by a simple mechanism. Stern-Volmer plots are linear and the photostationary trans/cis ratio is 2.0, independent of 1,3-pentadiene pressure over the range 2–180 Torr. The energy of the BPOL triplet state is less than but near 53 kcal mol^?1. It excites the s-cis 1,3-pentadiene rotamers exclusively. The decay ratio of the s-cis triplets is 3.75.     

Regiodivergent sulfonylarylation of 1,3-enynes via nickel/photoredox dual catalysis

Catalytic difunctionalization of 1,3-enynes represents an efficient and versatile approach to rapidly assemble multifunctional propargylic compounds, allenes and 1,3-dienes. Controlling selectivity in such addition reactions has been a long-standing challenging task due to multiple reactive centers resulting from the conjugated structure of 1,3-enynes. Herein, we present a straightforward method for regiodivergent sulfonylarylation of 1,3-enynes via dual nickel and photoredox catalysis. Hinging on the nature of 1,3-enynes, diverse reaction pathways are feasible: synthesis of α-allenyl sulfones via 1,4-sulfonylarylation, or preparation of (E)-1,3-dienyl sulfones with high chemo-, regio- and stereoselectivity through 3,4-sulfonylarylation. Notably, this is the first example that nickel and photoredox catalysis are merged to achieve efficient and versatile difunctionalization of 1,3-enynes.

A mild reaction protocol for regiodivergent sulfonylarylation of 1,3-enynes via dual nickel and photoredox catalysis has been developed, which led to efficient synthesis of α-allenyl sulfones or 1,3-dienyl sulfones.     

N,N-dihalophosphoramides-XV: The addition of diethyl N,N-dichlorophosphoroamidate (DCPA) to conjugated 1,3-dienes

The addition of DCPA to several conjugated 1,3-dienes has been studied. The reaction was found to proceed in dichloromethane and was spontaneously or photolytically initiated depending on the structure of the dienes. N-chloro adducts, formed upon addition, could be reduced “in situ” with sodium sulphite solution to give the corresponding diethyl N-(chloroalkenyl)posphoroamidates. Addition of DCPA to terminal double bond 1,3-dienes (butadiene, isoprene and 2,3-dimethyl-1,3-butadiene) leads regiospecifically to (E)-1,4-adducts. Similarly, 1,4-addition is also observed for 1,3-cyclohexadiene. Reaction of DCPA with nonterminal double bond 1,3-dienes (trans-piperylene, 4-methyl-1,3-pentadiene, 2,5-dimethyl-2,4-hexadiene and 1,4-diphenyl-1,3-butadiene) usually affords a mixture of adducts. Spectral data and chemical transformations pertinent to the proof of structure of DCPA addition products are presented. A possible mechanism for the addition is discussed.     

Simple construction of fused and spiro nitrogen/sulfur containing heterocycles by addition of thioamides or thioureas on cycloalkenyl-diazenes: examples of click chemistry

New 1-cycloalkenyl-1-diazenes have been obtained in good yields from cyclic β-ketoesters and hydrazine derivatives. They furnished new cycloalkyl[d][1,3]thiazolines with thioamides or new spirocycloalkyl-thiazolinones with thioureas. Moreover they gave, with imidazolidine-2-thione and tetrahydropyrimidine-2-thione, new and interesting spiro[cycloalkyl-1,2′-imidazo[2,1-b][1,3]thiazole] or spiro[cycloalkyl-1,2′-[1,3]thiazolo[3,2-a]pyrimidine] derivatives, respectively. Cycloalkyl[d][1,3]thiazolines were useful for the further preparation of unknown thia-triaza-tricyclo derivatives. Novel hexahydro-1,3-benzothiazoles have been achieved by reaction of N,N′-dialkylthioureas on N-1-phenyl-2-(1-cyclohexenyl)-1-diazene-1-carboxyamide. The acidic hydrolysis of spirocycloalkyl-thiazolinones produced 2-imino-5-(ω-carboxyalkyl)-4-thiazolidinones.     

A novel sulfonic acid functionalized ionic liquid catalyzed multicomponent synthesis of 10,11-dihydrochromeno[4,3-b]chromene-6,8(7H,9H)-dione derivatives in water

Three-component reactions of 4-hydroxycoumarin, aldehydes, and cyclic 1,3-dicarbonyl compounds were prompted by novel sulfonic acid functionalized ionic liquids 1,3-dimethyl-2-oxo-1,3-bis(4-sulfobutyl)imidazolidine-1,3-diium hydrogen sulfate ([DMDBSI]·2HSO₄) in water at reflux temperature to provide a novel series of 10,11-dihydrochromeno[4,3-b]chromene-6,8(7H,9H)-dione derivatives for the first time in high yields.