Stepwise oxidation of the stannole dianion

Tin oxidation of stannole dianion 1 with 1.3 equivalents of oxygen gave terstannole-1,3-dianion 3. The non-aromatic nature of 3 was confirmed by X-ray crystallographic analysis. Treatment of 1 with 1,2-dibromoethane (3 equiv) gave poly(1,1-stannole) 4, the formation of which was proven by reduction of 4 with lithium to revert to the starting dianion 1. Reaction of 1 with 1,2-dibromoethane (3 equiv) in the presence of phenyllithium gave phenyl-capped ter(1,1-stannole) 7. The electronic absorption spectra of newly obtained stannoles were also measured.     

Homo- and heterocomplexes of sodium and lithium amides--structures in solution

Addition of the chiral amine (S)-methyl(1-phenyl-2-pyrrolidinoethyl)[15N]amine (1) to a large excess of nBuNa resulted in the formation of a mixed sodium amide/nBuNa complex. This is the first observation of such a complex. Addition of nBuLi to the chiral sodium amide dimer 3 gave a new mixed lithium/sodium amide 5. The use of 15N,6Li coupling constants showed that the lithium in 5 occupied the tetracoordinated site. The use of chiral sodium amide 3 in the desymmetrization of cyclohexene oxide gave a modest enantiomeric excess (ee) of 37%. The corresponding lithium amide gave an ee of 70% of the same enantiomer. This is the first example of the comparison of asymmetric induction by sodium as cation with that of lithium.     

(-)-(R)- and (+)-(S)-Carvone in the Synthesis of Optically Active Acetylenic Alcohols,Ethers, and Dichlorosilyl Derivatives

Reaction of butyllithium with acetylene and 1-hexyne gave the corresponding lithium acetylides which reacted with (-)-(R)- and (+)-(S-carvone in a stereospecific fashion to give lithium (1-ethynyl- or 1-hexynyl)-5-isopropenyl-2-methyl-2-cyclohexenolates. Hydrolysis of the latter gave individual optically active tertiary terpene alcohols having both acetylenic and p-menthene fragment. Their treatment with methyl iodide in the presence of hexamethylphosphoric triamide afforded the corresponding methyl ethers. The reaction of 3-ethynyl-5-isopropenyl-3-methoxy-2-methylcyclohexene with butyllithium and trichloro(vinyl)silane yielded optically active dichlorosilyl-containing acetylenic compounds.     

Studies related to carba-pyranoses: a radical decarboxylation approach to monocarba-disaccharides

(1--> 1), (1--> 3) and (1--> 4) acetal-linked monocarba-disaccharides have been synthesised from a series of glucosylated gamma- and delta-lactonic acids prepared from common intermediate, obtained from the Diels-Alder reaction of maleic anhydride and (E)-1-(2',3',4',6'-tetra-O-acetyl-beta-D-glucopyranosyloxy)-3-(trimethylsiloxy)buta-1,3-diene 1. Thiohydroxamic ester 14, prepared from gamma-lactonic acid 9, gave, upon treatment with tert-butyl thiol and light, the lactone 15. Subsequent lithium aluminium hydride reduction and acetylation gave the (1--> 3) acetal-linked monocarbadisaccharides 1,6-di-O-acetyl-3-O-(2',3',4',6'-tetra-O-acetyl-beta-D-glucopyranosyl)-2,4-dideoxy-5a-carba-beta-L-threo-hexopyranose 16. In a similar manner, protected monocarba-disaccharides 13, 19, 30, and 35 possessing L-ido, L-xylo, D-arabino and L-ido configurations of the carba-pyranose ring have been prepared. Treatment of thiohydroxamic esters 14 and 17 with either tert-butyl thiol or trityl thiol, dimethyl sulfide, oxygen and light gave alcohols 20 and 22. Subsequent lithium aluminium hydride reduction and aceytlation gave the monocarbadisaccharides 1,4,6-tri-O-acetyl-3-O-[2',3',4',6'-tetra-O-acetyl-beta-D-glucopyranosyl]-2-deoxy-5a-carba-beta-L-arabino-hexopyranose 21 and 1,2,4,6-tetra-O-acetyl-3-O-(2',3',4',6'-tetra-O-acetyl-beta-D-glucopyranosyl)-5a-carba-beta-L-glucopyranose 23 respectively.     

Reactions of methylcopper and chiral organocuprates with 1-nitro-2-phenylethene and of lithium dimethylcuprate with methyl 3(nitrophenyl)propenoates

Organocopper compounds like methylcopper, lithium dimethylcuprate, chiral lithium methyl-(S)-2(1-dimethylaminoethyl)-phenylcuprate and lithium menthoxy(methyl)cuprate react with 1-nitro-2-phenylethene to give the conjugate addition product 1-nitro-2-phenylpropane in moderate yields. In the reaction with lithium methyl-(S)-2(1-dimethylaminoethyl)phenylcuprate 2% asymmetric induction was obtained. The reaction between lithium dimethylcuprate and methyl 3(4-nitrophenyl)propenoate gave the corresponding azoxy compound and no conjugate addition product, while methyl 3(3-nitrophenyl)propenoate gave some conjugate addition.     

A facile synthesis of pyrazole-5-sulfonamide derivatives

The reaction of the 5-unsubstituted pyrazoles 2a-k with lithium diisopropylamide or n-butyllithium gave intermediary 5-lithiopyrazoles, whose reaction with sulfur dioxide afforded the lithium pyrazole-5-sulfinates 3a-k . Subsequent reaction of 3a-k with N-chlorosuccinimide followed by ammonolysis provided the pyrazole-5-sulfonamides 5a-k .     

钯催化下(Z)-3-碘-3-三氟甲基-1-芳基烯丙醇与末端炔 烃的偶联反应

在Pd(PPh~3)~4/CuI催化下和使用1mol的NEt~3作碱和THF作溶剂,(Z)-3-碘-3-三氟甲基-1-芳基烯丙醇(1)与末端炔烃(3)反应得到正常的偶联产物5。当以NEt~3作碱和溶剂,Pd(PPh~3)~4/CuI催化1与3的交叉偶联反应生成化合物4。4为正常偶联化合物5在NEt~3存在下双键发生重排反应的产物。     

Facile Synthesis of Dibenzopentalene Dianions and Their Application as New π‐Extended Ligands

Reduction of phenyl(silyl)ethynes with potassium followed by quenching with iodine gave dibenzopentalenes in moderate yields. The intermediates of the reactions, dipotassium dibenzopentalenides, were isolated. The first dibenzopentalene–transition‐metal complex was successfully synthesized. The ruthenium atoms are located above the six‐membered rings. However, X‐ray diffraction analysis and theoretical calculations revealed that the aromatic nature of the five‐membered rings was retained. The cyclic voltammetry of the Ru complex revealed two oxidation waves with relatively large separation.     

1,3,2-Diazaborolyl-functionalized thiophenes and dithiophenes: synthesis, structure, electrochemistry and luminescence

Reaction of 2-bromo-1,3-diethyl-1,3,2-benzodiazaborole (1) with equimolar amounts of thienyl lithium or 2,2-dithienyl lithium led to the generation of benzodiazaboroles 2 and 3 which are functionalized at the boron atom by a 2-thienyl or a 5-(2,2-dithienyl) unit. Similarly 2-bromo-1,3-diethyl-1,3,2-naphthodiazaborole (4) and thienyl lithium or 2,2-dithienyl lithium afforded the naphthoborolyl-substituted thiophene 5 or dithiophene 6. Treatment of 2,5-bis(dibromoboryl)-thiophene 7 with 2 eq. of tBuN=CH-CH=NtBu in n-hexane followed by sodium amalgam reduction of the obtained bis(diazaborolium) salt 8 gave the 2,5-bis(diazaborolyl)thiophene 9. The 2,5-bis(diazaborolidinyl)-thiophene 10 resulted from the cyclocondensation of 7 with 2 eq. of N,N-di-tert-butylethylenediamine in the presence of NEt3. Analogously, cyclocondensation of 7 with N,N-diethylphenylenediamine gave the bis(benzodiazaborolyl) functionalized thiophene 11. The novel compounds were characterized by elemental analysis and spectroscopy (1H-, 11B-, 13C-NMR, MS and UV-VIS). The molecular structure of 3 was elucidated by X-ray diffraction. Cyclovoltammograms show an irreversible oxidation wave at 298-598 vs. Fc/Fc+. The borolylated thiophenes and dithienyls show intense blue luminescence with Stokes shifts of 30-107 nm.     

Reaction of 3-chloroallyltrimethylsilane with acid chloride and exploitation of a new regioselective synthesis of αβ-unsaturated epoxide

α-Chloro-βγ-unsaturated ketone (2) was synthesized from the reaction of 3-chloroallyltrimethylsilane (1) with acid chloride. The ketone was converted into αβ-unsaturated epoxide (3) regioselectively in good yield via reduction with NaBH₄ or LiAlH₄ followed by treatment with NaOH. Treatment with methyl lithium instead of reduction gave homologous epoxide (5).     

Synthetic studies in steroidal sapogenins and alkaloids—XII : Synthesis of sceptrumgenin and isonuatigenin

The Michael adduct of 5-nitro-2,2-ethylene-dioxypentan-1-ol acetate with E-5,17(20)-pregnadien-3β-ol-16-one gave on reduction with sodium borohydride and deketalisation, spirost-5-en-3β-ol-25-one. This intermediate was converted to sceptrumgenin through reaction with triphenyl phosphonium methylide and to isonuatigenin by treatment with dimethyl oxosulfonium methylide followed by lithium aluminium hydride.     

Synthesis of 3-(N-alkylamino)acetophenones via a benzyne intermediate

Reaction of 2-(2-bromophenyl)-2-methyl-1,3-dioxolane with lithium (1,1-dimethylethyl)amide, lithium (2,2-dimethylpropyl)amide, lithium (1,1-dimethylpropyl)amide gave the corresponding N-(alkyl)-3-(2-methyl-1,3-dioxolan-2-yl)benzenamines in moderate yields. 1-[3-[(1,1-Dimethylethyl)amino]phenyl]ethanone ( 4 ) was prepared in over 80% yield from 2-(2-bromophenyl)-2-methyl-1,3-dioxolane ( 2 ).     

1-Acetamido-17-carbomethoxydihydrothebainone

Treatment of 1-(5′-benzyloxy-4′-methoxy-2′-nitrobenzyl)-3,4-dihydroisoquinoline 2 with lithium/ammonia followed by the addition of ethanol gave a mixture of the dibenz[b,g]indolizines 3 and 4 . Omission of ethanol resulted in the formation of 3 only. The dihydroisoquinoline from 3,4-dimethoxyphenylethyl amine behaved similarly. Reduction of 2a with sodium/ammonia resulted in cleavage to give the nitro-guaiacol 8. Oxidation of 2a in the presence of potassium t-butoxide gave a complex mixture from which the benzoyldihydroisoquinoline 5 and 2-benzyloxy-5-nitroanisole were isolated in low yield. Treatment of the hexahydrobenzylisoquinoline 10 with diazotized sulfanilic acid, followed by reduction and then acetylation gave a diacetyl compound 12 which was hydrolyzed to 13. Ring closure with boron trifluoride gave the dihydrothebainone 14.     

Intermolecular Michael addition of substituted amines to a sugar-derived alpha,beta-unsaturated ester: synthesis of 1-deoxy-D-gluco- and -L-ido-homonojirimycin, 1-deoxy-castanospermine and 1-deoxy-8a-epi-castanospermine

The synthesis of polyhydroxylated piperidine alkaloids, namely, 1-deoxy-D-gluco-homonojirimycin 3a, 1-deoxy-L-ido-homonojirimycin 3b, and indolizidine alkaloids 1-deoxy-castanospermine 5a and 1-deoxy-8a-epi-castanospermine 5b, has been achieved. The key step involved is the intermolecular Michael addition of benzylamine to alpha,beta-unsaturated ester 1, derived from D-glucose, which afforded diastereomeric mixture of beta-amino esters 6a and 6b with D-gluco- and L-ido- configuration at C5, respectively. Attempts were made to increase and/or alter the diastereoselectivity at the newly generated stereocenter. The high stereoselectivity, in favor of L-ido-isomer 6b, was achieved under kinetically controlled conditions by using lithium N-benzyl amide as a Michael donor. The beta-amino esters 6a and 6b represent common intermediates to target molecules. Thus, LAH reduction of 6a and 6b, individually, gave beta-amino alcohol 7a and 7b. Sequential hydrogenolysis, selective protection of the amino group, followed by hydrolysis of the 1,2-acetonide functionality, and hydrogenation gave 3a and 3b, respectively. On the other hand, the beta-amino ester 6a was converted to gamma-amino ester 13a by Arndt-Eistert synthesis, which on hydrogenolysis and treatment with sodium acetate gave gamma-lactam 14a. The LAH reduction afforded pyrrolidene. The N-protection-hydrolysis-hydrogenation cascade successfully executed, and 1-deoxy-castanospermine 5a was obtained in good yield. The same sequence of reactions was applied to beta-amino ester 6b, which afforded 1-deoxy-8a-epi-castanospermine 5b.     

Reactions of 8-methyl-5-methylsulfanylmethyl-3-thiabicyclo-[3.3.1]non-7-en-6-one at the carbonyl group

The reduction of 8-methyl-5-methylsulfanylmethyl-3-thiabicyclo[3.3.1]non-7-en-6-one with aluminum hydride, lithium tetrahydridoaluminate, or lithium tris(tert-butoxy)hydridoaluminate in tetrahydrofuran gave 8-methyl-5-methylsulfanylmethyl-3-thiabicyclo[3.3.1]non-7-en-6-ol. 8-Methyl-5-methylsulfanylmethyl-3-thiabicyclo[3.3.1]nonan-6-ol was obtained by reduction of the title compound with sodium tetrahydridoborate in pyridine or dimethylformamide. The reaction of 8-methyl-5-methylsulfanylmethyl-3-thiabicyclo[3.3.1]non-7-en-6-one with hydroxylamine hydrochloride afforded the corresponding oxime.     

Heterocyclic systems. 1. Synthesis of 5,6,6a,7,8,13-hexahydroquinoxalino[2,1-c][1,4]benzodiazepine

The intramolecular cyclization of 1-(2-aminobenzoyl)-2-carbethoxy-3-oxo-1,2,3,4-tetrahydroquinoxaline, followed by lithium aluminum hydride reduction, gave the title compound.     

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.     

Reaction of perfluorocyclopentene with various carbon nucleophiles--heteroaromatic lithium reagents, enolate and phosphonium ylide

The addition of heteroaromatic lithium reagents 2 to a THF solution of perfluorocyclopentene (1) provided preferentially the corresponding monosubstituted products 5, while the addition of 1 to 2 effectively gave the 1,2-disubstituted products 6 in good to excellent yields. The reaction of 1 with sodiomalonate 3 or phosphonium ylide 4 also proceeded smoothly to form the 1,3-disubstituted product 8 or 10 in high yield, respectively.     

Stereodefined synthesis of O3'-labeled uracil nucleosides. 3'-[(17)O]-2'-Azido-2'-deoxyuridine 5'-diphosphate as a probe for the mechanism of inactivation of ribonucleotide reductases

Thermolysis of a 2'-[(16)O]-O-benzoyl-[(17)O]-5'-O-(tert-butyldimethylsilyl)-O(2),3'-cyclouridine derivative gave the more stable 3'-[(17)O]-O-benzoyl-[(16)O]- 5'-O-(tert-butyldimethylsilyl)-O(2),2'-cyclouridine isomer, which was converted into 3'-[(17)O]-2'-azido-2'-deoxyuridine by deprotection and nucleophilic ring opening at C2' with lithium azide. The 5'-diphosphate was prepared by nucleophilic displacement of the 5'-O-tosyl group with tris(tetrabutylammonium) hydrogen pyrophosphate. Model reactions gave (16)O and (18)O isotopomers, and base-promoted hydrolysis of an O(2),2'-cyclonucleoside gave stereodefined access to 3'-[(18)O]-1-(beta-D-arabinofuranosyl)uracil. Inactivation of ribonucleoside diphosphate reductase with 2'-azido-2'-deoxynucleotides results in appearance of EPR signals for a nitrogen-centered radical derived from azide, and 3'-[(17)O]-2'-azido-2'-deoxyuridine 5'-diphosphate provides an isotopomer to perturb EPR spectra in a predictable manner.     

The chemistry of a ketene-sulfur dioxide adduct

We have demonstrated the formation of a reactive species from ketene and sulfur dioxide and have investigated some of its reactions. The 3 + 2 ← 5 cycloaddition reactions of this intermediate with benzylideneaniline and its derivatives gave the corresponding 2,3-diphenylthiazolidin-4-one 1,1-dioxides. The reduction of 2,3-diphenylthiazolidin-4-one 1,1-dioxide with lithium aluminum hydride yielded the corresponding thiazolidine. Aniline and its derivatives reacted with the ketene-sulfur dioxide adduct to give thioaceto-1,3-dianilide 3-oxide. o-Phenylenediamine gave [2,1,5]benzothiadiazepin-4-one 2-oxide, a derivative of a new ring system, [2,1,5]benzothiadiazepine. o-Aminophenol yielded [1,2,5]benzothiazepin-4-one 2-oxide.