Yamamoto condensation

Patents of Dow Chemicals first described 9,9-diaryl-substituted PF homopolymers 204 and 205 by Yamamoto polymerization of the corresponding 2,7-dibromo monomers [272], although the methods for monomer preparation were not described. For unsubstituted fluorenone, a convenient method for its conversion into 9,9-(4-hydroxyphenyl)-[307-309] and 9,9-(4-alkoxyphenyl)fluorenes [310] was reported previously, which included condensation of fluorenone with phenol or its ethers in acidic conditions (dry HC1 [308,309] or H2SO4 [307,311]) in the presence of (3-mcrcaptopropionic or mercaptoacetic acids. Both polymers 204 and 205 showed similar Mn 21,000 with PDI of 1.48 and 1.75, respectively, and spectral data typical for PF (205 Aabs = 389 (r 50,000 //(mol cm) APL = 417, 439, and 473 mn (THF)) (Chart 2.48). 

A side reaction occurring with acetaldehyde and higher aldehydes containing a-hydro-gens is aldol condensation [Hashimoto et al., 1976, 1978 Yamamoto et al., 1978], Aldol reaction can be extensive at ambient temperatures and higher but is avoided by polymerization at low temperature. 

Another type of aldol condensation using cyclic enol ethers was demonstrated by Yamamoto and co-workers in which the condensation of tributyl (1-cyclohexene-1-yloxy)stannane 154 with benzaldehyde proceeded in 74% yield, as shown in Figure 9.48. The ratio of anti product 155 to syn product 156 was 36 64 with an anti ee of 84% (Fig. 9.48). 

The palladium catalyzed benzannulation reaction, described by Yamamoto, was successfully extended to the synthesis of condensed pyranone derivatives. The precursor to the cyclization underwent the benzannulation spontaneously under the applied Sonogashira coupling conditions (8.40.) on formation, to give the desired dibenzo />,ri pyranone. The functionalities tolerated in the process include unsaturated bonds and polar functional groups, such as hydroxyl.52... 

Recently, Yamamoto et al. have shown that the chiral acyloxyborane complex 31 is an excellent catalyst for the asymmetric Mukaiyama condensation of simple silyl enol ethers (Scheme 8B1.19 Table 8B1.11 entries 1-7) [43], The syn-aldol adducts are formed preferentially with high enantiomeric excess regardless of the stereochemistry (EI7) of the silyl enol ethers, suggesting an extended transition state (entries 4, 7). This methodology has been... 

W. Kob, C. Brangian, T. Stuhn, and R. Yamamoto, in Computer Simulation Studies in Condensed Matter Physics XIII, D. P. Landau, S. P. Lewis, and H. B. Schttler, eds., Springer, Berlin, 2000. 

Saito, S. Shiozawa, M. Yamamoto, H. Mixed crossed aldol condensation between conjugated esters and aldehydes using aluminum... 

T. Yamamoto A8.6 Osaka University, Department of Condensed Matter Physics Institute of Scientific and Industrial Res., Osaka 567, Japan... 

Y. Sekiguchi, A. Matsunaga, A. Yamamoto and Y. Inoue (2000). Analysis of condensed phosphates in food products by ion chromatography with an on-line hydroxide eluent generator. J. Chromatogr., 881, 639-644. 

Conceptually this new three-component reaction resembles the methods applied by Steglich, Enders et al. [8a] and Yamamoto et al. [8b], who treated the preformed iminoesters 26 and 29 at low temperature with the electron-rich olefins 27 and 30, respectively [9]. However, the use of boronic acid derivatives appears to be a versatile method with a great deal of potential. As Petasis and Zavialov note at the end of their paper, unprotected amino acids and peptides, aryl boronic acids, and chiral boronates can also participate in their three component condensation [7a]. Transition metal catalysis also... 

Discoveries made in the late 1970s of electrical conductivity in conjugated polymers spawned a monumental interest in the study of these materials, which are ideally suited for synthesis via cross-coupling reactions. Yamamoto was the first to realize this possibility with a regiochemicahy defined synthesis of poly(/ -phenylene) formed via the Kumada-Corriu protocol. Since then, various cross-coupling reactions have been applied in condensation polymerization reactions,with the Suzuki and Sonogashira protocols gaining the most widespread use. 

Wharton et al. (42) showed that filter paper over which virgin female American cockroaches [Periplaneta americana (L.)] had crawled was highly attractive to males, and these investigators have very recently reported that they obtained from such papers 28 /xg. of an attractant which they were unable to identify. As the result of an independent investigation which was not sufficiently completed to be reported at the symposium held in September 1962 in Atlantic City, Jacobson, Beroza, and Yamamoto (24) isolated the sex attractant and identified it as 2,2-dimethyl-3-isopropylidenecyclopropyl propionate. The pure attractant, which elicits a response from males at levels below )Ltg., was obtained by condensing the air stream passed... 

Kouchi A., Yamamoto T., Kozasa T., Kuroda T., and Greenberg J. M. (1994) Conditions for condensation and preservation of amorphous ice and crystallinity of astro-physical ices. Astron. Astrophys. 290, KX19-1018. 

There has been a problem with the kind of carbon powder from the earliest times. Pine soot generally gives the largest pine needle-like sparks but sometimes we have a kind of soot which gives only small sparks. The reason is not clear at present. I.Yamamoto, one of manufacturers of Senko-Hanabi, said that the sparks appear with considerable difference depending on the place where the soot condenses during production. 

Yamamoto et al. [2] made a condensation calculation to estimate tlie chemical composition of the ice in molecular clouds and cometaiy nuclei. They assumed tlie interstellar molecular composition for tlie abundance of gas. Inter-... 

Yamamoto has investigated the intra-molecular condensation of y-(alkoxy)allylstaimanes with aldehydes as a general approach for the stereocontrolled synthesis of polycyclic ethers (Scheme 5.2.26). The strategy has been iteratively applied to the total synthesis of hemibrevetoxin B. i In this fashion, the Lewis acid-promoted reaction of 122 leads to formation of seven-membered ether 123, which is transformed into 124 for intra-molecular allylation to the fused-oxepane 125. 

Iketaki, Y., Watanabe, T., Ishiuchi, S., Sakai, M., Omatsu, T., Yamamoto, K. and Watanabe, T. (2003) Investigation of the fluorescence depletion process in the condensed phase application to a tryptophan aqueous solution. Chem. Phys. Lett., 372, 773-778. 

Other important aldol condensations are the Mukaiyama-type aldol reactions of silyl enol ethers with aldehydes that usually require catalyst activation. Yamamoto reported that such reactions under high pressure proceed (i) without catalyst even at room temperature, (ii) without isomerization of the formed adducts and (iii) with a reversed synlanti stereoselectivity compared with that of the TiCU-catalysed reactions. ... 

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