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Volume 56, Issue 5
Displaying 1-12 of 12 articles from this issue
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Masakatsu SHIBASAKI, Takehiko IIDA, Yoichi M. A. YAMADA1998 Volume 56 Issue 5 Pages 344-356
Published: May 01, 1998
Released on J-STAGE: January 28, 2010
JOURNAL FREE ACCESSThis article focuses on a new concept in catalytic asymmetric synthesis, which was first realized by the use of heterobimetallic complexes. As such complexes function at the same time as both a Lewis acid and a Brønsted base, similar to enzymes, they make possible a variety of efficient catalytic asymmetric reactions. This “heterobimetallic” concept has proven to be applicable to a variety of new asymmetric catalyses. We have already succeeded in asymmetric nitroaldol reactions catalyzed by the LaLi3tris (binaphthoxide) complex (LLB) and asymmetric Michael reactions catalyzed by the LaNa3tris (binaphthoxide) complex (LSB). Now the LLB catalyst could also be applied efficiently to the tandem inter-intramolecular asymmetric nitroaldol reaction, affording a synthetically useful bicyclic product with four newly generated chiral carbons in one pot. Furthermore we succeeded in the first direct asymmetric aldol reactions of aldehydes with unmodified ketones (up to 94% ee) by using a catalytic amount of LLB. While LLB was also effective in the hydrophosphonylation of aldehydes, asymmetric hydrophosphonylations of imines were efficiently catalyzed by the LnK3tris (binaphthoxide) complex (LnPB : Ln = rare earth metal such as La, Yb) (up to 96% ee). On the other hand, alkali metal free lanthanum complexes prepared from Ln (O-i-Pr) 3 (Ln = La or Yb) and 1, 1'-binaphthol (BINOL) or 3- hydroxymethyl-BINOL were excellent catalysts for the asymmetric epoxidation of α, β-unsaturated ketones (up to 94% ee). We also developed another type of heterobimetallic catalysts featuring group 13 elements such as Al or Ga as a central metal. Among them, the AlLibis (binaphthoxide) complex (ALB) is an effective catalyst for asymmetric Michael reactions of malonates or Horner-Wadsworth-Emmons reagents (up to 99% ee) and for asymmetric tandem Michael-aldol reactions. Applications of this catalyst to syntheses of biologically important compounds such as 11-deoxy-PGF1a, and tubifolidine are also described. Furthermore the GaLibis (binaphthoxide) complex (GaLB) in combination with molecular sieves 4 A was found to be an efficient catalyst for asymmetric ring openings of a variety of epoxides with t-BuSH (up to 97% ee).View full abstractDownload PDF (1835K) -
Shû KOBAYASHI, Haruro ISHITANI1998 Volume 56 Issue 5 Pages 357-367
Published: May 01, 1998
Released on J-STAGE: November 16, 2009
JOURNAL FREE ACCESSThe Lewis acid-mediated reactions of imine are one of the most powerful methods for preparation of nitrogen-containing compounds. However, there are few examples of the reactions using catalytic amounts of Lewis acids, because the strong coordination of the products (which are mostly secondly or tertiary amines), deactivates the acids. This article introduces several types of new achiral and chiral Lewis acids which can mediated the reactions of imines catalytically. The essence of the catalytic activation of imines by Lewis acids is the equilibrium between Lewis acids and bases (imines or products), and it has been revealed that rare earth triflates (lanthanide and scandium trifluoromethanesulfonate) are excellent catalysts for this purpose. Imino-aldol reactions, aza Diels-Alder reactions, allylation reactions, cyanation reactions, and three-component reactions of aldehydes, amines, and nucleophiles were successfully carried out in the presence of catalytic amounts of rare earth triflates. Polymer-supported reagents also worked well by using the triflates as catalysts. In addition, it was shown that group IV triflates (Zr and Hf triflates) were effective for catalytic activation of imines. The first truly catalytic asymmetric reactions of imines have been achieved using new chiral Lewis acids. In the presence of a catalytic amount of a chiral rare earth catalyst, imines derived from 2-aminophenol and aldehydes reacted with cyclopentadiene or vinyl ethers to afford 8-hydroxytetrahydroquinoline derivatives in high yields with high diastereo- and enantioselectivities. Moreover, the first catalytic enantioselective Mannich-type reactions of imines with silyl enolates using a novel chiral zirconium catalyst have been developed. High levels of enantioselectivities in the synthesis of chiral β-amino ester derivatives, β-amino alcohol derivatives, and tetrahydropyridine derivatives have been achieved using these reactions.View full abstractDownload PDF (1453K) -
New Guidelines for Structural Design of Chiral CatalystShuji KANEMASA, Yoji ODERAOTOSHI1998 Volume 56 Issue 5 Pages 368-376
Published: May 01, 1998
Released on J-STAGE: January 28, 2010
JOURNAL FREE ACCESSCationic aqua complexes of a trans-chelating tridentate ligand, (R, R) -4, 6-dibenzofurandiyl-2, 2' -bis (4-phenyloxazoline), and transition metal (II) perchlorates are effective catalysts in the cyclopentadiene Diels-Alder reactions, nitrone cycloadditions, and diazomethane cycloadditions with 3-alkenoyl- 2-oxazolidinones to show excellent enantioselectivities. The active catalyst complex prepared from nickel (II) perchlorate hexahydrate has an octahedral structure with three aqua ligands, and it can be isolated and stored for months without loss of catalytic activity. The aqua complex prepared from Ni (II) or Zn (II) perchlorate results in highly effective chiral amplification in the Diels-Alder reaction. Two mechanisms for amplification are involved for this remarkable chiral amplification : (1) precipitation of S4-symmetric meso-2 : 1 complex between DBFOX/Ph and Ni (II) ion, and (2) associative formation of 1 : 1 heterochiral complexes by the aid of hydrogen bonds based on aqua ligands to produce stable meso oligomers.View full abstractDownload PDF (1325K) -
Takashi OOI, Naoki ASAO, Keiji MARUOKA1998 Volume 56 Issue 5 Pages 377-385
Published: May 01, 1998
Released on J-STAGE: November 16, 2009
JOURNAL FREE ACCESSCarbonyl group is one of the most popular and yet ubiquitous functionality of organic compounds and often encountered in biomolecules such as peptides and lipids, playing a crucial role to organize three dimensional intermolecular associations. For organic chemists, it always appears as an extremely useful functional group to be manipulated and either Bronsted acids or Lewis acids are routinely employed for the activation of carbonyls in electrophilic substitution reactions, where the acids preferably coordinate to one of the two carbonyl lone pairs. Being close to the core of Lewis acid chemistry, we have been interested some time in the possibility of double electrophilic activation of carbonyl functionality by designing bidentate Lewis acid catalysts which could simultaneously coordinate to both of the carbonyl lone pairs with two metals. In this review, we describe the development of bidentate aluminum and titanium Lewis acids, and evaluation of their reactivity and selectivity in organic synthesis. Further, the applications of our concept to the elaboration of new synthetic methodologies are also discussed. Those include neutral allylation of carbonyls with bidentate tin compounds by using chelation-induced Lewis acidity, and activation of bidentate bis (silyl) compounds with a fluoride anion.View full abstractDownload PDF (1050K) -
Kazuhiko SAIGO, Atsushi SUDO, Yukihiko HASHIMOTO1998 Volume 56 Issue 5 Pages 386-394
Published: May 01, 1998
Released on J-STAGE: November 16, 2009
JOURNAL FREE ACCESSIn recent years, the development of chiral auxiliaries has been attracting much attention. Although many of these are usually derived from natural chiral compounds, limitations in their structural modification are sometimes an obstacle to achieve an efficient asymmetric process. This problem would be solved by using non-natural chiral compounds due to their two favorable characteristics in contrast to natural products and their derivatives : 1) Both enantiomers are readily available and can be used in asymmetric reactions. 2) The structure can be freely designed.
In the preparation of well-designed, non-natural chiral auxiliaries, the optical resolution of their racemic modifications is thought to be one of the most practical methods. In this context, the development of an efficient method for the optical resolution of a racemic modification is considered to be essential. We have been carrying out a study which was coherent with the design, optical resolution, and application of non-natural chiral auxiliaries. In this review we would like to describe our recent results concerning the development of new non-natural chiral auxiliaries as well as their application to asymmetric syntheses.View full abstractDownload PDF (1158K) -
Hiroyuki NAKAMURA, Yoshinori YAMAMOTO1998 Volume 56 Issue 5 Pages 395-405
Published: May 01, 1998
Released on J-STAGE: November 16, 2009
JOURNAL FREE ACCESSπ-Allylpalladium complexes have an electrophilic character and have been widely utilized for the catalytic C-C bond formation reaction with various nucleophiles in Organic Synthesis. We found that the reaction of allylic stannanes with aldehydes proceeded in the presence of palladium catalysts. Detailed investigation revealed that bis-π-allylpalladium complexes, which are a key intermediate in this reaction, have a nucleophilic character. This review describes the unprecedented reactions of the bis-π-allylpalladium complexes : (1) Catalytic allylation of aldehydes and imine. (2) Chemoselective allylation of imines in the presence of aldehydes. (3) Catalytic asymmetric allylation of imines. (4) Catalytic amphiphilic allylation.View full abstractDownload PDF (1311K) -
Masahiro MURAKAMI, Kenichiro ITAMI, Minoru UBUKATA, Itaru TSUJI, Yoshi ...1998 Volume 56 Issue 5 Pages 406-412
Published: May 01, 1998
Released on J-STAGE: November 16, 2009
JOURNAL FREE ACCESSDevelopment of new cycloaddition reactions of conjugated allenes catalyzed by transition metal complexes is described. In the first place, the synthesis and structures of vinylallene-rhodium complexes were investigated. (Vinylallene) rhodium complexes of three kinds of coordination modes, that is, η2-coordination, η4-coordination, and planar σ2-coordination, were selectively synthesized by facile ligand substitution of the Wilkinson's complex with vinylallenes of different substitution patterns. The endo-exo isomerization observed with the η4-complex suggested a considerable contribution from the metallacyclic form. This structural study led us to develop a new carbonylative [4+1] cycloaddition reaction of vinylallenes, which was further extended to a highly enantioselective synthesis of 2- (alkylidene) cyclopentenone. Next, the intermolecular directed [4+2] cycloaddition of a vinylallene with an ordinary 1, 3-diene was achieved by the use of a palladium (0) catalyst. An excellent specificity observed between the vinylallene geometries and the cycloadduct stereostructures was explained by assuming a mechanism involving a (π-allyl) palladium intermediate. The iridium-catalyzed carbonylative [5+1] cycloaddition reaction was also developed, wherein a six-membered cyclohexenone skeleton was assembled from allenylcyclopropane and carbon monoxide.View full abstractDownload PDF (960K) -
Nobuharu IWASAWA1998 Volume 56 Issue 5 Pages 413-423
Published: May 01, 1998
Released on J-STAGE: November 16, 2009
JOURNAL FREE ACCESSThe addition reaction of organolithium or Grignard reagents to silyl-substituted Fischer-type carbene complex gives either (E) - or (Z) -vinylsilanes with high selectivities depending on the reaction conditions.
A new type of propargyl metallic species is generated by the addition reaction of alkynyllithiums with Fischer-type carbene complexes. These species act as regiochemically well-behaved propargyl metallic species and react with various electrophiles to give five-membered heterocyclic compounds. This reaction was applied to a concise enantioselective total synthesis of (-) -PI-091.
Variable temperature NMR studies of the reaction of the propargyl tungsten species with electrophiles revealed that 1, 2-migration of pentacarbonyltungsten occurs to generate a vinyl metallic species. Highly efficient method was developed for the preparation of a variety of synthetically useful, fully substituted five-membered heterocyclic compounds by the iodine-oxidation of the intermediates produced from Fischer-type carbene complexes, alkynes, and various carbon electrophiles.View full abstractDownload PDF (1329K) -
Fumie SATO, Hirokazu URABE, Sentaro OKAMOTO1998 Volume 56 Issue 5 Pages 424-432
Published: May 01, 1998
Released on J-STAGE: November 16, 2009
JOURNAL FREE ACCESSTreatment of Ti (O-i-Pr) 4 with 2 equiv of i-PrMgX (X =Cl or Br) provides (η2-propene) Ti (O-i-Pr) 2 in essentially quantitative yield. This new low-valent titanium complex nicely acts as a versatile titanium (II) equivalent to effect the following unique transformations. Thus, alkynes afforded titaniumalkyne complexes which, in turn, react with aldehydes, ketones, or imines to furnish the corresponding addition products. Allylic or propargylic compounds such as halides and alcohol derivatives gave allylic- or allenylic titanium species, which could be utilized in chemo- and diastereoselective reactions with carbonyl compounds. While acetylenic esters resulted in an intramolecular nucleophilic acyl substitution (INAS) reaction to provide unsaturated ketones, olefinic ones furnished cyclopropanols. 1, 6- or 1, 7-Dienes, enynes, and diynes underwent cyclometallation to give dialkoxytitanacycles, which show some distinctive reactivities among the metallacycles of early transition metal complexes. A few applications to natural product synthesis by taking advantage of these methods are also illustrated.View full abstractDownload PDF (1112K) -
Miwako MORI1998 Volume 56 Issue 5 Pages 433-442
Published: May 01, 1998
Released on J-STAGE: November 16, 2009
JOURNAL FREE ACCESSEnyne metathesis is unique and interesting in synthetic organic chemistry. The reaction is catalyzed by various transition metals such as Cr, Mo, W, Ru, Pd, and Pt. There are two types for enyne metathesis one is caused by [2+2] cycloaddition of a multiple bond and transition metal carbene complex, and the other is an oxidative cyclization reaction caused by low-valent transition metals. In usually, this reaction is used as intramolecular enyne metathesis because it is difficult to control intermolecular enyne metathesis. Intramolecular enyne metathesis is designated as an alkylidene migration reaction since an alkylidene part of alkene migrates to an alkyne carbon. Many cyclic compounds having the diene moiety, which are very useful in organic synthesis, were synthesized using this method. Recently, intermolecular enyne metathesis has been developed between an alkyne and ethylene as novel diene synthesis.View full abstractDownload PDF (1024K) -
Naoto CHATANI, Shinji MURAI1998 Volume 56 Issue 5 Pages 443-452
Published: May 01, 1998
Released on J-STAGE: November 16, 2009
JOURNAL FREE ACCESSTransition-metal-catalyzed carbonylation with cleavage of a C-H bond is described. The reactions described are (1) carbonylation at the C-H bond α to the ring nitrogen in imidazoles (ii) carbonylation at the C-H bond γ to the ring nitrogen in pyridylbenzenes, aromatic imines, and aryloxazolines (iii) carbonylation at the olefinic C-H bond in pyridylolefines (iv) carbonylation at the sp2 C-H bond in a piperazine ring. Coordination of a directing group such as nitrogen or oxygen functionalities to transition metals, such as ruthenium and rhodium, promotes site selective cleavage of a C-H bond.View full abstractDownload PDF (1166K) -
[in Japanese], [in Japanese], [in Japanese], [in Japanese]1998 Volume 56 Issue 5 Pages 453
Published: May 01, 1998
Released on J-STAGE: November 16, 2009
JOURNAL FREE ACCESSDownload PDF (180K)
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