Browsing by Author "Lee, ASY"

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Chemoselective deprotection of acid labile primary hydroxyl protecting groups under CBr4-photoirradiation conditions
(2004-12-06)
Chen, MY
;
Patkar, LN
;
Lu, KC
;
Lee, ASY
;
Lin, CC
The CBr4-photoirradiation in methanol generates a controlled source of HBr, which can chemoselectively deprotect commonly used hydroxyl-protecting groups in saccharides and nucleosides, such as tert-butyldimethylsilyl, isopropylidene, benzylidene and triphenyl ethers in the presence of other acid-labile functional groups. (C) 2004 Elsevier Ltd. All rights reserved.
Synthesis of beta-amino esters by regioselective amination of allyl bromides with aryl and alkyl amines
(2005-08-19)
Chen, HY
;
Patkar, LN
;
Ueng, SH
;
Lin, CC
;
Lee, ASY
One of the two possible regioisomers can be exclusively formed by combining a suitable solvent and a specific amount of triethylamine as a base during the amination of allyl bromide 5. The S(N)2' product 7 was produced using dichloromethane as a solvent and triethylamine (7 equiv) as base; S(N)2 product 6 was predominantly generated in hexane with 0.5 equivalents of triethylamine. Furthermore, a new reaction condition for the efficient cyclization of 7 to yield alpha-methylene beta-lactam 8 using Sn[N(TMS)(2)](2) as a reagent, is disclosed.