Heterocyclic analogs of pleiadiene

2,3-Dihydro derivatives of perimidine were obtained in high yields by the action of lithium aluminum hydride or sodium borohydride on perimidinium salts and 1,3-dialkylperimidones.     

Mannich reaction in a number of six-membered heterocyclic γ,-ketones. X. Stereochemistry of the reduction and phenylation of 2, 2-dimethyl-5-dimethylaminomethyl-4-oxotetrahydropyran

2, 2-Dimethyl-5-dimethylaminomethyl-4-oxotetrahydropyran was subjected to reduction with lithium aluminum hydride, sodium borohydride, aluminum isopropoxide, and lithium in liquid ammonia, to catalytic hydrogenation over Raney nickel, and phenylation with phenyllithium. The quantitative ratios in the resulting mixtures of stereoisomeric 2, 2-dimethyl-5-dimethylaminomethyl-4-hydroxytetrahydropyrans and their dependence on the character of the reducing agents were established by means of gas — liquid chromatography and PMR spectroscopy. The individual geometrical isomers of the amino alcohols were isolated, and their three-dimensional structures were studied by means of their PMR and IR spectra.See [1] for communication IX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 611–616, May, 1976.     

Titanium‐mediated living radical styrene polymerizations. V. Cp2TiCl‐catalyzed initiation by epoxide radical ring opening: Effect of solvents and additives

The effects of solvents, additives, ligands, and solvent in situ drying agents as well as catalyst and initiator concentrations have been investigated in the Cp₂TiCl‐catalyzed radical polymerization of styrene initiated by epoxide radical ring opening. On the basis of the solubilization of Cp₂Ti(III)Cl and the polydispersity of the resulting polymer, the solvents rank as follows: dioxane ≥ tetrahydrofuran > diethylene glycol dimethyl ether > methoxybenzene > diphenyl ether ≥ bulk > toluene ? pyridine > dimethylformamide > 1‐methyl‐2‐pyrrolidinone > dimethylacetamide > ethylene carbonate, acetonitrile, and trioxane. Alkoxide additives such as aluminum triisopropoxide and titanium(IV) isopropoxide are involved in alkoxide ligand exchange with the epoxide‐derived titanium alkoxide and lead to broad molecular weight distributions, whereas similarly to strongly coordinating solvents, ligands such as bipyridyl block the titanium active site and prevent the polymerization. By contrast, softer ligands such as triphenylphosphine improve the polymerization in less polar solvents such as toluene. Although mixed hydrides such as lithium tri‐tert‐butoxyaluminum hydride, sodium borohydride, and lithium aluminum hydride react with bis(cyclopentadienyl)titanium dichloride to form mixed titanium hydride species ineffective in polymerization control, simple hydrides such as lithium hydride, sodium hydride, and especially calcium hydride are particularly effective as in situ trace water scavengers in this polymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2015–2026, 2006     

Ring opening reaction of N-substituted dihydropyrimidines with metal hydride complexes

N-Substituted dihydropyrimidines, 1, 3 , and 4 , easily afforded N,N′-disubstituted 2,4-diaminopentanes 2 in good yield by the ring opening reaction with sodium borohydride. The reaction with lithium aluminum hydride was also examined.     

Reduction of substituted 1H-4,5-dihydroimidazolium salts

Reactions of several substituted 1H-4,5-dihydroimidazolium salts 1 with nucleophilic and electrophilic reducing agents acting via hydride transfer were explored. Reaction of compounds 1 with lithium aluminum hydride in THF afforded the corresponding imidazolidines 2 . When alkaline borohydrides (sodium borohydride, potassium borohydride, sodium cyanoborohydride) in ethanol at room temperature were used, partial or total over-reduction of compounds 2 leading to N,N,N'-trisubstituted ethylenediamines took place on occasion. Results may be explained taking into account that reductive cleavage of 2 proceeds via a stabilized iminium ion present in protic solvents. Treatment of compounds 1 with an excess of borane in THF afforded the corresponding imidazolidines 2 or their borane complexes, according to the substituent type.     

Mono-substitution of iron pentacarbonyl metal hydride: facilitation

Controlling the degree of substitution of iron pentacarbonyl with neutral ligands has usually been difficult. Conditions are reported whereby considerable control may be exercised over the substitution of iron pentacarbonyl; with PPh₃ the ratio of mono-/disubstitution may be varied over a range of 50. The substituted iron carbonyl complexes were obtained by treating iron pentacarbonyl with lithium aluminum hydride or sodium borohydride in refluxing THF in the presence of a variety of neutral ligands. The method is particularly useful for a simple high yield synthesis for monosubstituted iron carbonyls.     

Behavior of triethyloxonium fluoborate toward hydride-ion donors

Summary Triethyloxonium fluoborate reacts with sodium borohydride and with lithium aluminum hydride to give ethane, and does not react with dioxane, ethyl alcohol, benzyl alcohol or tropilidene.     

Heterocyclic systems. II. Synthesis of 4H,6H-pyrrolo[1,2-a][4,1]benzoxazepine

The reduction of 1-(2-methoxycarbonylphenyl)pyrrole-2-carboxaldehyde by lithium aluminum hydride led to 1-(2-hydroxymethylphenyl)-2-hydroxymethylpyrrole, which was in turn transformed into 4H,6H-pyrrolo-[1,2-a][4,1]benzoxazepine through intramolecular dehydration. The reductive action of sodium borohydride, instead, allowed the preparation of 6-oxo-4H-pyrrolo[1,2-a][4,1]benzoxazepine.     

Reduction studies on benzaza[3.3.3]propellanc derivatives

Sodium borohydride reduction of 3-methyl-2,3-dioxo-7,8-benzo-3-aza[3.3.3]propellan-6-one (1b) gave 2,4-dioxo-3-methyl-7,8-benzo-3-aza[3.3.3]propellan-6-ol, while lithium aluminum hydride reduction gave 3-methyl-7,8-benzo-3-aza[3.3.3]propellan-6-ol, which on oxidation, gave the corresponding ketone. This ketone formed the corresponding thioketal upon reaction with 1,2-ethanedithiol. Raney nickel desulfurization of the thioketal provided 3-methyl-6,7-benzo-3-aza[3.3.3]propellane. The same compound was also obtained in poor yield by forming the thioketal of Ib followed by lithium aluminum hydride reduction and Raney nickel desulfurization of the product. Desulfurization of the thioketal of Ib gave 2,4-dioxo-6,7-Benzo-3-aza[3.3.3]propellane.     

Reduction of 4-hydroxy-3, 5-dialkylbenzaldehydes with complex hydrides of alkali metals

Conclusions A study was made of the reduction of seven 4-hydroxy-3,5-dialkylbenzaldehydes with aluminum lithium hydride and sodium borohydride.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1311–1313, June, 1971.     

Aziridinyl ketones XVII. The hydrogenation of 2-phenyl-3-aroylaziridines to aziridinylcarbinols

The sodium borohydride reduction of both cis and trans-1-cyclohexyl-2-phenyl-3-aroylaziridines provides in each case the corresponding carbinol as a mixture of the two possible diastereoisomeric racemates, whereas reduction of these ketones with lithium aluminum hydride or with lithium diisopropylamide provides only the racemate resulting from attack on the carbonyl group from the least hindered side. Catalytic hydrogenation of a cis aziridinyl ketone cleaved the aziridine ring and provided an amino carbinol.     

Mannich reaction in six-membered heterocyclic γ-ketones

The stereochemical principles of the reduction of 2,2-dimethyl-5-aminomethyl-4-oxotetrahydropyrans with lithium aluminum hydride, sodium borohydride, aluminum isopropoxide, and lithium in liquid ammonia were investigated by determination of the dependence of the quantitative ratio of the resulting epimeric amino alcohols in the mixtures on the character of the reducing agent and its concentration and the nature of the solvent. The individual geometrical isomers of the amino alcohols were isolated, and their structures were established by PMR and IR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 318–323, March, 1978.     

Reductive opening of the thiazolidine ring. Selective N-methylation of cysteamines

The reaction of thiazolidines 2 and 7 with borane was investigated. It gave N-methylcysteamines 3 and 8 through thiazolidine ring opening. Sodium borohydride and lithium aluminum hydride were ineffective.     

Cubane derivatives 7. Synthesis and molecular structure of 4-bromo-1-hydroxymethylcubane

The present study concerned with reduction of methyl 4-bromocubanecarboxylate (1) with lithium aluminum hydride and aluminum hydride in THF. An efficient procedure was developed for the synthesis of 4-bromo-1-hydroxymethylcubane (2) based on reduction of compound 1 with aluminum hydride under mild conditions. The structure of 2 was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1461–1464, June, 2005.     

The reductive ring opening of some derivatives of isatin

Treatment of two isatin-3-imines, 3-isopropyIamino-1-methylindoline-2-one and 3-cyclohexylamino-1-methylindolin-2-one with sodium borohydride produced the fully-reduced anilines 2-isopropylamino-2-(2-methylaminophenyl) ethanol and 2-cyclohexylamino-2-(2-methylaminophenyl) ethanol, respectively. Reductive ring-opening of derivatives of isatin is not observed in related examples when either catalytic or lithium aluminum hydride reduction are employed and it is concluded that the present effect is dependant upon the softness of sodium borohydride as a reducing agent.     

Asymmetric synthesis of (alphaR)-polyfluoroalkylated prolinols based on the perfluoroalkyl-induced highly stereoselective reduction of perfluoroalkyl N-Boc-pyrrolidyl ketones

Reduction of the obtained chiral (S)- tert-butyl 2-(perfluoroalkanoyl)pyrrolidine-1-carboxylate with sodium borohydride or lithium aluminum hydride proceeded smoothly to give the corresponding (S)- tert-butyl 2-((R)-perfluoro-1-hydroxyalkyl)pyrrolidine-1-carboxylate in yields of 73-97% with excellent diastereoselectivities (up to >98% de), compared with the reduction of nonfluorinated (S)-tert-butyl 2-pentanoylpyrrolidine-1-carboxylate.     

New diazadi(and tri)thia‐21‐crown‐7 ethers containing 8‐hydroxyquinoline side arms

A series of macrocyclic diazadi(and tri)thiacrown ethers containing two 5‐substituent‐8‐hydroxyquinoline side arms have been synthesized from the corresponding macrocyclic diazadi(and tri)thiacrown ethers. The crown ethers were obtained by reduction of the proper macrocyclic di(and tri)thiadiamides by borane‐tetrahydrofuran or by sodium borohydride‐boron trifluoride ethyl etherate‐tetrahydrofuran. The yields for the reduction of diamides by sodium borohydride‐boron trifluoride ethyl etherate‐tetrahydrofuran were higher than those by borane‐tetrahydrofuran. The following four methods were used to prepare macrocycles bearing two 8‐hydroxyquinoline side arms: (1) Mannich reaction with 8‐hydroxyquinoline; (2) Reductive animation with 8‐hydroxyquinoline‐2‐carboxaldehyde using sodium triacetoxyborohydride as the reducing agent; (3) Cyclization of N,N'‐bis(8‐hydroxyquinolin‐2‐ylmethyl)‐1,2‐bis(2‐aminoethoxy)ethane (38) with bis(α‐chloroamide) 5 ; and ( 4 ) A step‐by‐step process wherein macrocyclic trithiadiamide 11 was reduced by lithium aluminum hydride‐tetrahydrofuran to the cyclic monoamide 36 , which smoothly reacted with 5‐chloro‐8‐hydroxyquinoline to produce monosubstituted‐macrocyclic monoamide 39 .     

Synthesis,structure, and acylation of dihydroquinopimaric acid hydroxy derivatives

Reduction conditions of methyl dihydroquinopimarate with sodium borohydride and lithium aluminum hydride were established. As a result of the reduction 14β-hydroxy, 17α-hydroxy, 14β,17α-dihydroxy, and 14β,17α,21α-trihydroxy derivatives were obtained. The structure of methyl esters of 14β-acetoxy- and 17α-hydroxydihydroquinopimaric acid was established by XRD and NMR methods. Mono-, di-, and triacylates were obtained from the diterpene alcohols.     

Chemical and electrochemical reduction of some pyrazolo[1,5-a]pyrimidines

Various pyrazolo[1,5-a]pyrimidines 1 are prepared by two different ways. Their chemical reduction by sodium borohydride leads generally to 4,5,6,7-tetrahydro compounds 3, while lithium aluminum hydride yields 4,7-dihydro derivatives 2 at room temperature, and 3 in refluxing tetrahydrofuran. A complex mixture of oxidizable hydrodimers is obtained by electrochemical reduction. An electroreduction at a more negative potential also gives 4,7-dihydro compounds 2. A new 4,5-dihydropyrazolo[1,5-a]pyrimidine has been obtained by condensation of 5-amino-3-methyl-1H-pyrazole with acetophenone.     

Ring opening reaction of 1,2-diaryl-3-methyl-1,4,5,6-tetrahydropyrimidinium salts with metal hydride complexes

The reaction of a series of 1,2-diaryl-3-methyl-1,4,5,6-tetrahydropyrimidinium iodides 1 with reducing agents acting by hydride ion transfer was studied. With excellent yields alkaline borohydrides readily reacted to form N'-aryl-N-benzyl-N-methyltrimethylenediamines 3 by reductive cleavage of the intermediate hexahydropyrimidine 2 . Ring opening is explained by the formation of a stabilized iminium ion, which also accounts for the cyclic aminal 2 hydrolysis observed in alcoholic solution after gradual addition of borohydride. Reactions with lithium aluminum hydride or with borane failed to render satisfactory results due to insolubility of the salt in solvents commonly employed. Comparisons are made with the behaviour of 1H-4,5-dihydroimidazolium salts which were studied in an earlier paper.