Tomioka studies

In the same context, Tomioka et al. have studied the addition of Me2CuLi to chalcone in the presence of another chiral sulfonamide, depicted in Scheme 2.26, which provided the corresponding 1,4-product in a good yield but with a low enantioselectivity (8% ee). In addition, these authors have obtained both moderate yield and enantioselectivity (<28% ee) for the addition of ZnEt2 to 2-cyclohexenone performed in the presence of a chiral bis(sulfonamides) ligand depicted in Scheme 2.26. ... 

This key paper was followed by a flurry of activity in this area, spanning several years." " "" A variety of workers reported attempts to deconvolute the temperature dependence of carbene singlet/triplet equilibria and relative reactivities from the influence of solid matrices. Invariably, in low-temperature solids, H-abstraction reactions were found to predominate over other processes. Somewhat similar results were obtained in studies of the temperature and phase dependency of the selectivity of C-H insertion reactions in alkanes. While, for example, primary versus tertiary C-H abstraction became increasingly selective as the temperature was lowered in solution, the reactions became dramatically less selective in the solid phase as temperatures were lowered further. Similar work of Tomioka and co-workers explored variations of OH (singlet reaction) versus C-H (triplet reaction) carbene insertions with alcohols as a function of temperature and medium. Numerous attempts were made in these reports to explain the results based on increases in triplet carbene population... 

Tomioka, H. Matsushita, T. Benzoxetene. Direct observation and theoretical studies. Chem. Lett. 1997, 399 100. 

This report prompted further study of asymmetric dihydroxylation, and higher enantioselect-ivity has been realized with various C2- or quasi-C2-symmetric diamines as the chiral auxiliaries.168-174 One example reported by Tomioka and Koga is shown in Scheme 43.170 Although the reaction is highly enantioselective, it needs the use of stoichiometric 0s04 and chiral diamine, because the diamine coordinates Osvl ion strongly and retards its reoxidation to Osvm ion. 

The so-called blue and red phases of polydiacetylenes have been extensively investigated. Thus, for example, Tomioka et al. [214] studied the... 

The formation of carbon-carbon bonds by conjugate addition of carbonucleophiles to a,/3-unsaturated systems has been studied intensively and reviewed over the past few years . Interestingly, applications with simple, unstabilized lithium enolates are relatively rare. Most reported examples are limited to the addition of stabilized enolates, such as those derived from malonates or acetoacetates. Nevertheless, some diastereo- and enantioselective versions of the conjugate addition, even with unstabilized lithium enolates, are well known. In 2004, Tomioka and coworkers studied the influence of a chiral diether (191) on the 1,4-addition of lithium ester enolates (189) to a,-unsaturated ketones (equation 51) . Their investigations showed that good enantioselectivities were obtained with cyclic enones, like 2-cyclopentenone (190) addition to a mixture of 189 and 191 gave the desired 1,4-adduct (R)-192 with 74% ee, but only 47% yield. Unfortunately, also the Peterson product 193 was formed in a yield of 22% by initial 1,2-addition of the enolate to the Michael acceptor. 

H. Sato, A. Matsuzaki, S. Nishio, M. Yoshimi, K. Yamamoto, and H. Tomioka, A Raman Spectroscopic study of merocyanine aggregates of a N-15 isomer of 6-nitro BIPS. A direct evidence for the association through the NOj bridges, Chem. Lett. 8, 715-716 (1996). 

The first report of enantioselective addition of organometallic reagents to an azomethine function appeared in 1990. Tomioka and co-workers reported the addition of organohthium compounds to J -arylimines in the presence of a stoichiometric amount of a chiral P-amino ether as the asymmetric controller [19a]. This significant contribution resulted from an observation made earlier in the context of a related synthetic project [20aj. Tomioka et al. studied the addition of methylhthium (MeLi) and -butyllithium ( -BuLi) to unsaturated N-(4-methoxyphenyljimines derived from benzaldehyde (2a), cinnamaldehyde (2b),... 

Tomioka N, Itai A. GREEN a program package for docking studies in rational drug design. J Comput-Aided Mol Des 1994 8 347-366. 

We add to these investigations a recent study of Tomioka s group (Hirai et al., 1994), in which reaction of O2 was used for trapping a triplet carbene and where it was possible to observe the triplet carbene at ambient temperature by laser flash photolysis. (2,4,6-Tri( err-butyl)phenyl)phenyldiazomethane (8.51) afforded photo-lytically 4,6-di( er butyl)-l,l-dimethyl-3-phenylindan (8.53) almost quantitatively. It is an insertion of the intermediate carbene into a CH bond of the tert-hMiy group at C(2). No solvent adducts were found in benzene, cyclohexane or methanol. As... 

An interesting intramolecular oxidation was found by Tomioka et al. (1992b) when studying the photochemistry of (2-nitrophenyl)diazomethane (8.56) in an argon matrix at 10 K. Irradiation at A > 350 nm provided 2-nitrosobenzaldehyde (8.57), presumably as a result of intramolecular reduction of the nitro group with the neighboring carbene center (8-32). ... 

As reactions of carbenes in organic glasses were discussed in this and other sections of this chapter we close this section with a short reference to a very interesting review of Tomioka (1994) of which we became aware when this chapter was already submitted to the publisher. Tomioka emphasizes strongly a caveat against extrapolations from solution results and from liquid phase mechanistic rules to matrix conditions. This can be shown, for example, in the stereospecificity of cyclopropanations of insertion products into the allylic CH bonds of alkenes. Studying Tomioka s review is clearly a must for all chemists who work with carbenes in a matrix ... 

Enantioselective additions of organoUthiums to epoxides, oxetanes and cyclic acetals, have been reported by Tomioka, Alexakis and Muller during these studies the compatibility of BF3-Et20, to assist ring-openings, with sparteine was demonstrated [36]. 

Tomioka, Y. Mochiike, A. Himeno, J. Yamazaki, M. Studies on aromatic nitro compounds, I, Reaction of 6-nitroquinobne with active methylene compounds in the presence of bases. Chem. Pharm. Bull. 1981, 29, 1286-1291. 

N. Tomioka and A. Itai, /. Comput.-Aided Mol. Desipi, 8,347 (1994). GREEN A Program Package for Docking Studies in Rational Drug Design. 

When studying the addition of the lithium enolate of menthyl acetate to p-methoxyphenyl imines like 359, Tomioka and coworkers noticed a remarkable LDA effect the diastereoselectivity was found substantially higher when a second equivalent of LDA was present in this variant of the Mannich addition, so that diastereomeric ratios up to 97 3 were reached. A condensation under formation of P-lactams was not observed instead, N-protected P-amino esters were isolated [183]. 

In 1997, Adam and coworkers reported another variation of C2 symmetric ether linked ketones using mannitol (15) and tartaric acid (16) as chiral backbones (Scheme 3.14) [19]. Up to 81% ee was obtained. In 2001,Tomioka and coworkers reported epoxidations with C2 symmetric 7-membered sulfonylamide ketones 17 and 18 (Scheme 3.15) [16, 20]. Up to 30% ee was obtained for stilbene with 17b. In their subsequent studies, higher ee values were obtained with tricycHc ketone 19 and bicyclic ketone 20 (Scheme 3.16) [21]. For the epoxidation of 1-phenylcyclohexene, a quantitative yield and 83 % ee were obtained with a catalytic amount (20 mol%) of ketone 19. 

Tomioka, H., Matrix isolation study of reactive o-quinoid compounds generation, detection and reactions. Pure Appl. Chem., 69, 837, 1997. 

Murata, S., Kobayashi, I., Kongou, C., Miyata, M., Matsushita, T., and Tomioka, H., Remarkable wavelength-dependent photoreactions of the bis(diazo)ketone having inequivalent diazo groups studies in fluid solutions and in low-temperature matrixes, /. Org. Chem., 65, 6082, 2000. 

---