Ester derivatives, application transfer

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. 

APPLICATIONS OF PHOTOINDUCED ELECTRON TRANSFER PROCESSES TO KETONE, ALDEHYDE, AND ESTER DERIVATIVES IN ORGANIC SYNTHESIS... 

A similar approach was reported by Lygo and co-workers who applied comparable anthracenylmethyl-based ammonium salts of type 26 in combination with 50% aqueous potassium hydroxide as a basic system at room temperature [26, 27a], Under these conditions the required O-alkylation at the alkaloid catalyst s hydroxyl group occurs in situ. The enantioselective alkylation reactions proceeded with somewhat lower enantioselectivity (up to 91% ee) compared with the results obtained with the Corey catalyst 25. The overall yields of esters of type 27 (obtained after imine hydrolysis) were in the range 40 to 86% [26]. A selected example is shown in Scheme 3.7. Because the pseudo-enantiomeric catalyst pairs 25 and 26 led to opposite enantiomers with comparable enantioselectivity, this procedure enables convenient access to both enantiomers. Recently, the Lygo group reported an in situ-preparation of the alkaloid-based phase transfer catalyst [27b] as well as the application of a new, highly effective phase-transfer catalyst derived from a-methyl-naphthylamine, which was found by screening of a catalyst library [27c],... 

Alkylations. Highly enantioselective alkylation of t-butyl 4,4-bis (p-dimethyl-aminophenyl)-3-butenoate and t-butyl A -diphenylmethyleneglycine in the presence of a quatemized cinchona alkaloid results. The salt plays a dual role in asymmetric induction and as a phase-transfer catalyst. The products from the former reaction can be cleaved at the double bond to furnish chiral malonaldehydic esters which have many obvious synthetic applications. A combination of PTC, LiCl, and an organic base (e.g., DBU) favors the enantioselective alkylation of a chiral A-acylimidazolidinone in which the acyl side chain is derived from glycine. ... 

Another very recent application of radical addition to isonitriles is the radical-mediated imidoylation of telluroglycosides 47 [25], These compounds were found to react with isonitriles under photothermal conditions to give 1-telluroimido-glycosides 48 through an atom transfer radical reaction (Scheme 20). Products 48 can be further transformed into imidic esters and 1-acyl glycosides, a class of derivatives that are part of important biologically active compounds. 

PET processes between earbonyl derivatives (A) and amines (D) have received considerable attention since the pioneering studies on photoreduction of aromatic ketones with tertiary amines. Numerous developments have appeared during the last 20 years. The purpose of this review is to consider recent applications of PET processes of carbonyl and ester groups and to discuss the influence of the chemical environment on the scope of the reactions and their synthetic development. Furthermore, several reactions such as the photolysis of sulfonyl derivatives, which have been reexamined in connection with electron transfer processes, will also be described. Finally, where possible, a comparison of the photochemical process with similar reactions carried out in the ground state will be made. 

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