Synthesis and oxidation of 1,1,2,2-tetramethyl-3,4,5,6-tetraphenyl-1,2-disila-3,4-cyclohexadiene

The synthesis of 1,1,2,2-tetramethyl-3,4,5,6-tetraphenyl-1,2-disila-3,4-cyclohexadiene, (I), from 1,4-dilithiotetrapheynylbutadiene and 1,2-dichlorotetramethyldisilane is described. (I) is reluctant to react with singlet oxygen, in contrast to its carbon analogue, but the SiSi bond of(I) is readily oxidized to give 2,2,7,7-tetramethyl- 3,4,5,6-tetrapheynyl-1-oxo-2,7-disila-3,5-cycloheptadiene. The mechanism of the formation of this siloxane is discussed, and a peroxy radical shown to act as an important intermediate in the oxidation.     

Hydroacridines and related compounds

3,3-Dimethyl-2-oxa-1,2,3,4-tetrahydroacridine and its N-oxide and 3,3,6,6-tetramethyl-2,7-dioxa-sym-octahydroacridine N-oxide were synthesized. On heating with acetic anhydride, the N-oxides form, respectively, acetates of 3,3-dimethyl-2-oxa-1,2,3,4-tetrahydro-4-acridinol and 3,3,6,6-tetramethyl-2,7-dioxa-sym-octahydro-4-acridinol. Hydrolysis of the acetates gives the alcohols themselves. Oxidation of 3,3,6,6-tetramethyl-2,7-dioxa-sym-octahydro-4-acridinol acetate gives the corresponding N-oxide. Oxidation of 3,3,6,6-tetramethyl-2,7-dioxa-sym-octahydro-4-acridinol with manganese dioxide gives 3,3,6,6-tetramethyl-2,7-dioxa-sym-octahydro-4-acridinone.See [9] for communication VII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1218–1221, September, 1971.     

Ring-closing metathesis for the synthesis of novel 9- and 10-membered silicon-containing benzo-fused heterocycles

A ring-closing metathesis (RCM) strategy afforded a number of novel 9- and 10-membered benzo-fused compounds containing at least one silicon atom as part of the heterocyclic portion. In this manner, the following compounds containing heterocyclic rings of 9-10 atoms were synthesized: (Z)-2,2-dimethyl-7-[(4-methylphenyl)sulfonyl]-2,3,6,7-tetrahydrobenzo[h][1,7,2]oxazasilonine, (Z)-2,2-dimethyl-3,6-dihydro-2H-benzo[h][1,7,2]dioxasilonine, (Z)-8-isopropoxy-9-methoxy-3,3-dimethyl-1,3,4,7-tetrahydrobenzo[g][1,2]oxasilonine and (Z)-2,2,7,7-tetramethyl-2,3,6,7-tetrahydrobenzo[i][1,8,2,7]dioxadisilecine.     

Selective and recyclable palladium porphyrins-catalyzed oligomerization of tert-butyl acetylene in environment-friendly ionic liquids

Efficient and selective palladium porphyrins-catalyzed olimerization of tert-butyl acetylene to form (3Z,5Z)-2,2,7,7-tetramethyl-3,6-dihalo-3,5-octadiene has been developed in environment-friendly ionic liquids. The reaction proceeded readily with effective recycling of the ionic liquids and easy isolation of the products.     

溶剂对钯催化的叔丁基乙炔低聚反应化学选择性的调控作用

报道了溶剂对钯催化的叔丁基乙炔低聚反应化学选择性的调控作用. 反应可在苯-正丁醇双组分溶剂体系中顺利进行, 当双组分溶剂体系中苯占优势比例时, 反应发生递次的三分子炔烃顺式插入, 经由顺式s-烯钯中间体生成环三聚产物1,3,5-三叔丁基苯; 而当双组分溶剂中正丁醇组分上升至一定比例, 反应选择性生成(3Z,5Z)-2,2,7,7-四甲基- 3,6-二氯-3,5-辛二烯或(3Z,5Z)-2,2,7,7-四甲基-3,6-二溴-3,5-辛二烯, 这是由于正丁醇可显著加快C—Pd σ键的断裂, 并与叔丁基乙炔、σ-烯钯中间体形成弱氢键作用力, 同时也与Pd(II)和Cu(II)等离子存在配位效应. 在强极性质子溶剂H₂O中, 反应生成偶联双炔: 2,2,7,7-四甲基-3,5-辛二炔. 文中就反应溶剂体系、钯铜催化剂及反应可能机理等分别进行了探讨.     

New 7‐membered diazepanone alkoxyamines for nitroxide‐mediated radical polymerization

The synthesis of new 7‐membered diazepanone alkoxyamines [2,2,7,7‐tetramethyl‐1‐(1‐phenyl‐ethoxy)‐[1,4]diazepan‐5‐one ( 3 ) and 2,7‐diethyl‐2,3,7‐trimethyl‐1‐(1‐phenyl‐ethoxy)‐[1,4]diazepan‐5‐one ( 8 )] through the Beckmann rearrangement of piperidin‐4‐one alkoxyamines was developed. Both 3 and 8 were evaluated as initiators and regulators for the nitroxide‐mediated radical polymerization of styrene and n‐butyl acrylate. 8 , a sterically highly hindered alkoxyamine readily available as a crystalline solid, allowed the fast and controlled polymerization and preparation of polymers with low polydispersity indices (1.2–1.4) up to a degree of polymerization of about 100. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3332–3341, 2004     

Novel solvent-controlled chemoselective palladium/copper(II) halide catalyzed oligomerization of <Emphasis Type="Italic">tert</Emphasis>-butyl acetylene

Solvent-controlled chemoselective palladium-catalyzed oligomerization of tert-butyl acetylene is reported in this paper. The reaction was carried out smoothly in benzene/n-BuOH binary solvent system. When unpolar aprotic benzene was the preponderating component in the binary system, a cyclotrimerization process occurred to produce 1,3,5-tri-tert-butylbenzene via a mechanism of three acetylene molecules, inserted step by step, forming σ-butadienyl-Pd and σ-hexatrienyl-Pd intermediates. While when the polar, protic and strong coordinating component n-BuOH, which aids Cu(II) to cleave the C-Pd σ-bonds and solvate Pd(II), Cu(II) cations, halo anion, σ-butadienyl-Pd intermediate, etc., was increased to a certain extent in the binary solvent system, the reaction proceeded readily via a n-BuOH-promoted mechanism to give (3Z,5Z)-2,2,7,7-tetramethyl-3,6-dichloro-3,5-octadiene or (3Z,5Z)-2,2,7,7-tetramethyl-3,6-dibromo-3,5-octadiene, respectively. Possible weak hydrogen bonds and n-π weak force between n-BuOH (electron pair donor (EPD)) and tert-butyl acetylene (and σ-butadienyl-Pd intermediate, electron pair acceptor (EPA)) in the latter process were also in favor of the n-BuOH promoted pathway. Meanwhile, the coupling product 2,2,7,7-tetramethyl-3,5-octadiyne was exclusively obtained when the reaction was conducted in singular polar H₂O. Influences of the solvent, catalysts, as well as possible mechanism were discussed in this paper.     

Metathesis of allyl cyanide in the presence of a catalytic system containing tungsten hexachloride and 1,1,3,3-tetramethyl-1,3-disilacyclobutane

Conclusions The metathesis of allyl cyanide was carried out by the action of a catalytic system containing tungsten hexachloride by 1,1,3,3-tetramethyl-1,3-disilacyclobutane.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 920–921, April, 1988.     

Cyclization and rearrangements of diterpenoids. VIII. Products of dehydration of (1S,2S,7S,10R,11S,12S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.01,10.02,7]-pentadecan-11-ol by phosphorus oxychloride

On the dehydration of (1S, 2S, 7S, 10R, 11S, 12S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadecan-11-ol by phosphorus oxychloride in pyridine a mixture of three hydrocarbons is formed: the known (1R, 2S, 7S, 10S, 11R, 12S, 13S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7.0^11,13]pentadecane and the previously undescribed (1R, 2S, 7S, 10S, 11S)-2,6,6,10,12-pentamethyltetra-cyclo[9.2.2.0^1,10.0^2,7]pentadeca-12-ene and (1R, 2S, 7S, 10S, 11S)-2,6,6,10-tetramethyl-12-methylenetetracyclo[9.2.2.0^1,10.0^2,7]pentadecane, based on a new carbon skeleton.Institute of Chemistry, Moldavian SSR Academy of Sciences, Kishinev. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 489–497, July–August, 1989.     

Asymmetric synthesis of the carbocyclic nucleoside building block (R)-(+)-4-aminocyclopentenone using delta-amino beta-ketophosphonates and ring-closing metathesis (RCM)

Amino keto-2,7-dienes undergo ring-closing metathesis (RCM) to give 4-aminocyclopentenones, valuable intermediates in the asymmetric construction of carbocyclic nucleosides. The key amino ketodienes were prepared using delta-amino beta-ketophophonates, a new sulfinimine-derived chiral building block, and HWE chemistry. [reaction: see text]     

Cyclization and rearrangements of diterpenoids. VIII. Products of dehydration of (1S,2S,7S,10R,11S,12S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.01,10.02,7]-pentadecan-11-ol by phosphorus oxychloride

On the dehydration of (1S, 2S, 7S, 10R, 11S, 12S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7]pentadecan-11-ol by phosphorus oxychloride in pyridine a mixture of three hydrocarbons is formed: the known (1R, 2S, 7S, 10S, 11R, 12S, 13S)-2,6,6,10,12-pentamethyltetracyclo[10.2.1.0^1,10.0^2,7.0^11,13]pentadecane and the previously undescribed (1R, 2S, 7S, 10S, 11S)-2,6,6,10,12-pentamethyltetra-cyclo[9.2.2.0^1,10.0^2,7]pentadeca-12-ene and (1R, 2S, 7S, 10S, 11S)-2,6,6,10-tetramethyl-12-methylenetetracyclo[9.2.2.0^1,10.0^2,7]pentadecane, based on a new carbon skeleton.     

Metathesis of functional derivatives of olefins by the action of the WC16-1,1,3,3-tetramethyl-1.3-disilacyclobutane catalytic system

A study was carried out on the metathesis of esters of unsaturated carboxylic acids and nitriles by the action of the WC1₆ -1,1,3,3-tetramethyl-1,3- disilacyclobutane catalytic system. The possibility of efficient homometathesis and cometathesis with-olefins and allyltrimethylsilane was demonstrated for ethyl 4-pentenoate and ally1 cyanide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 172–176, January, 1990.     

Aryne chemistry—II Syntheses of some substituted triphenylenes via organometallic reagents derived from 4,4′-dimethyl-2-fluoro-2′-iodobiphenyl

Several possible mechanisms are considered for the formation of triphenylene and substituted triphenylenes in aryne reactions involving organometallic compounds. A stepwise rather than a concerted mechanism is favoured both from previous evidence and from present work. In particular, we have synthesized 2,7-dimethyl-; 1,6,11- and 2,6,11-trimethyl-; 1,3,6,11- and 2,3,6,11-tetramethyl-; and 6,11-dimethyl-2-methoxytriphenylene by way a biphenyl intermediate.     

A one pot, metathesis-hydrogenation sequence for the selective formation of carbon-carbon bonds

A combination of homogeneous hydrogenation and metathesis reactions allows highly efficient, stepwise chemo- and stereoselective formation of three separate 2,7-diaminosuberic acid derivatives in a single pot without isolation of intermediates.     

SYNTHESIS OF NOVEL BI-FUNCTIONAL COPOLYMER BEARING STERICALLY HINDERED PHENOL AND HINDERED AMINE GROUPS VIA RING-OPENING METATHESIS POLYMERIZATION

Norbornene derivatives exo,endo-2-[2-(3,5-di-tert-butyl-4-hydroxyphenoxy)-acetoxy]methyl-5-norbornene(M1) and 3,3,5,5-tetramethyl-4-piperidinyl 5-norbornene-exo,endo-2-carboxylate(M2)were synthesized and polymerized by RuCl_2(=CHPh)(PCy_3)_2 to prepare a novel kind of bi-functional polymer bearing sterically hindered phenol(SHP)and hindered amine(HLAS)groups via ring-opening metathesis polymerization(ROMP).The resulting copolymers were characterized by gel permeation chromatography(GPC),~1H-NMR and diffe...     

A short synthesis of the endogenous plant metabolite 7-hydroxyoxindole-3-acetic acid (7-OH-OxIAA) using simultaneous C–H borylations

Methyl indole-3-acetate undergoes two simultaneous iridium-catalysed borylations to deliver exclusively 2,7-diboronate, with the ligand 3,4,7,8-tetramethyl-1,10-phenanthroline (Me₄Phen) pivotal in driving the diborylation to completion. Subsequent oxidation-hydrolysis of the diboronate provides methyl 7-hydroxyoxindole-3-acetate which upon hydrolysis of the ester delivers 7-OH-OxIAA, an antioxidant, endogenous metabolite of indole-3-acetic acid found in various types of corn. This route has an overall yield of 50%, involves a single chromatographic purification and is an efficient alternative to existing syntheses, made possible by executing simultaneous oxidations at the indole C2 and C7 sites.     

Nicholas reactions in the construction of cyclohepta[de]naphthalenes and cyclohepta[de]naphthalenones. The total synthesis of microstegiol

The application of the Nicholas reaction chemistry of 2,7-dioxygenated naphthalenes in the synthesis of cyclohepta[de]napthalenes and in the synthesis of (±)-microstegiol (1) is presented. The substitution profile of Nicholas monosubstitution (predominantly C-1) and disubstitution reactions (predominantly 1,6-) on 2,7-dioxygenated napthalenes is reported. Application of a 1,8-dicondensation product and selected C-1 monocondensation products to the construction of cyclohepta[de]naphthalenes by way of ring closing metathesis and intramolecular Friedel-Crafts reactions, respectively, is described. Deprotection of the C-7 oxygen function to the corresponding naphthol allows tautomerization to cyclohepta[de]naphthalene-1-ones upon seven-membered-ring closure in most cases, and replacement of the C-2 oxygen function in the naphthalene by a methyl group ultimately allows the synthesis of (±)-microstegiol.     

Asymmetric synthesis of polyhydroxylated pyrrolizidines via transannular iodoamination with concomitant N-debenzylation

The doubly diastereoselective "matched" conjugate addition of lithium (R)-N-but-3-enyl-N-(α-methyl-p-methoxybenzyl)amide to tert-butyl (4S,5R,E)-4,5-O-isopropylidene-2,7-dienoate (derived from d-ribose in 3 steps) and in situ enolate oxidation with (-)-camphorsulfonyloxaziridine was followed by ring-closing metathesis with Grubbs I to give a hexahydroazocine scaffold. Subsequent treatment with I(2) resulted in transannular iodoamination accompanied by loss of the α-methyl-p-methoxybenzyl group to give the corresponding pyrrolizidine scaffold as a single diastereoisomer upon direct crystallization from the crude reaction mixture. Further functional group manipulations enabled the preparation of (-)-7a-epi-hyacinthacine A1.     

Migrastatin母核9-羟基的衍生化

为了将示踪元素引入Migrastatin母核并用于肿瘤诊断和靶向治疗,以2,6-二烯庚酸-5-(叔丁基二甲硅氧基)-6-甲氧基-2,4-二甲基-2,7-二烯酯为起始原料,经过脱TBS保护、酯化和烯烃复分解反应,成功地合成了Migrastatin母核9-甲磺酸酯,总收率15.3%,其结构经1H NMR和ESI-MS表征。