1-5-Benzoxazolyl

Demchenko et al. developed 1-5-benzoxazolyl (SBox) mannoside 23-25 as potent donors for the synthesis of -mannoside [40]. They demonstrated that an acyl or thiocarbamoyl group at the C-4 position gave a favorable effect, possibly by participating to the C-1 position. Nucleophilic attachment of an acceptor occurs predominantly from the y0-face [40] (O Scheme 15). 

Diterpentyl- 2- benzoxazolyl 5,7- Di lerpentyl - 2-benzoxazolyl. i,7-Di(erpentyl-2-henzoxaz.olyl 139 140 592... 

Chemical Name 2-(2-p-Chlorophenyl-5-benzoxazolyl)propionic acid... 

The 6-benzoxazolyl analog of the 5-benzoxazolyl product Is prepared as follows ... 

The residue was heated at 220°C until no more water was evolved, then was allowed to cool. This yielded ethyl 2-(2-p-chlorophenyl-6-benzoxazolyl)propionate. 

In general and as expected, brighteners of relatively small molecular size are most suitable for application by exhaustion. Less volatile compounds of larger molecular size tend to be preferred for pad-thermosol application or for incorporation in the polymer mass. Commercially important for exhaust application are the previously mentioned pyrene derivative 11.22, the naphthalimide 11.23, the bis(benzoxazolyl)ethene 11.35, the bis (benzoxazolyl) thiophene 11.36, the distyrylbenzene 11.37 and the stilbene bis (acrylic ester) derivative 11.38. Products of the 11.35 type show excellent light fastness but only moderate fastness to sublimation. In view of this volatility they can be used in the transfer printing of polyester. 

While halogenation and Sandmeyer reactions are suitable for preparation of oxazolyl halides, benzoxazolyl halides with halogen on the benzene ring moiety may be synthesized via other approaches. For instance, 5-halobenzoxazoles were prepared by treating 4-halo-2-aminophenols with trimethyl orthoformate and concentrated aqueous HC1 [6]. 

S-Benzoxazolyl (SBox) and, especially, S-thiazolinyl (STaz) moieties are sufficiently stable for use in anomeric protection. These derivatives can, however, be activated under mild conditions using silver triflate [114-118]. 

Novel sialosyl donors, S-benzoxazolyl and S-thiazolyl sialosides, have been synthesized [170], Both SBox and STaz sialosides proved to be excellent glycosyl donors... 

There have been efforts to form aromatic polyamides directly from diacids at moderate temperatures by using various phosphorus compounds for in situ activation of the carboxyl groups [Arai et al., 1985 Higashi and Kohayashi, 1989 Krigbaum et al., 1985]. A useful agent is diphenyl(2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate, which probably activates the carboxyl group by forming a mixed carboxylic-phosphoric anhydride [Ueda, 1999 Ueda et al., 1991]. 

Benzoxazolyl ethers can also be used in this reaction sequence but an amount of catalyst equivalent to 20-40% by weight of ether is necessary in the hydrogenolysis step. 

The benzoxazolo[3,2-a]quinazolin-5-ones (216) were prepared in excellent yields by two routes. In the first route, the two heterocyclic rings of 216 were consecutively formed when the disodium salts of N-(2-hydroxyphenyl)anthranilic acids (214) wre cyclized with two molar equivalents of cyanogen bromide. In the second versatile route, the pyrimidine ring of 216 was formed when A/-(2-benzoxazolyl)-2-fluorobenzamides (217) were thermally cyclized (81JHC287). 

Kaplan and Jortner [164] have observed dipole—dipole energy transfer between the second excited state of rhodamine 6G and 2,5-bis(5 -f-butyl-2-benzoxazolyl)thiophene in ethanol. The donor excited state lifetime was estimated to be 0.19 ps based on energy transfer by Forster kinetics. 

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