Burgess-reagent

The Burgess reagent [methyl N-(triethylammoniumsulfonyl)carbamate], a neutral, white ciystalline solid, is efficient at generating olefins from secondary and tertiary alcohols where the first-order thermolytic Ei (dining the elimination— the two groups leave at about the same time and bond to each other concurrently) mechanism prevails. 

Example 1, On primary alcohols, the hydroxyl group does not eliminate but rather undergoes substitution  

Name Reactions A Collection of Detailed Mechanisms and Synthetic Applications, 

9 Elolsworth, D. D. The Burgess Dehydrating Reagent. In Name Reactions for Functional Group Transformations, Li, J. J., Ed. Wiley Hoboken, NJ, 2007, pp 189-206. (Review). 

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Burgess Reagent (inner salt) JOC, 1973, 38, 26 occurs vis a syn elimination... 

A constant interest in the development of new rapid methodologies for the preparation of oxazole hbraries is motivated by their presence in numerous biologically active natural products. Janda and coworkers were hrst to show that oxazoles can be obtained by microwave-assisted treatment of polymer-bound a-acylamino-/f-ketoesters with Burgess reagent [68]. Hydroxybutyl-functionalized /anda/el resin was used for this investigation, with key steps being monitored by on-bead FT-IR. First, a resin-bound acetoacetate was pre-... 

Fig. 13 Synthesis of oxazoles on JandaJel. Reagents and conditions a toluene, alkyl acetoacetate (R0(C0)CH2C0R R =t-Bu), reflux, 6h or alkyl acetoacetate (R = Me, Et), toluene, LiC104, reflux, 6h fc dodecylbenzenesulfonyl azide, EtsN, toluene, rt, 16 h c benzamide, Rh2(oct)4, toluene, 65 °C, Ih rf Burgess reagent, pyridine, chlorobenzene, MW 100 °C, 15 min (or 80 °C, 4 h with conventional heating) e AICI3, piperidine, CH2CI2, rt, 16 h...

Schemes Synthesis of 1,3,4-oxadiazoles using PEG-bound Burgess reagent...

A direct conversion of the oxazoline (44) to the thiazoline (45) can be achieved by the thiolysis of the oxazoline (44) with H2S in methanol in the presence of triethylamine followed by cyclodehydration with Burgess reagent. This method is essentially free from racemisation and has been used in the transformation of peptide substrates <95TL6395>. 

In the context of preparing potential inhibitors of histone deacetylase, Vasudevan and a team from Abbott have described the cyclization of 1,2-diacylhydrazides to 1,3,4-oxadiazoles with Burgess reagent under microwave conditions (150 °C, 15 min) (Scheme 6.224 a) [232], A different approach was chosen by Natero and coworkers, who prepared 2-chloromethyl-l,3,4-oxadiazoles by treatment of acyl hydrazides with 1-chloro-2,2,2-trimethoxyethane (Scheme 6.224b) [401]. Here, the reagent was used as solvent and the mixture was heated by microwave irradiation at 160 °C for 5 min. 

In the preparation of novel 1,3,4-oxadiazoles 56 from 1,2-diacylhydrazines 55, Brain and coworkers [29] used a highly efficient cydodehydration assisted by use of micro-waves, in THF as solvent, using polymer-supported Burgess reagent (Scheme 8.21). 

Microwave irradiation coupled with polyethylene glycol)-supported Burgess reagent reduced the reaction time to 2-4 min and led to improved yields. Use of harsh reagents, e. g. SOCl2, POCl3, and polyphosphoric acid, for the cydodehydration were avoided. 

A set of heterocyclic ketones including 1,3,4-oxadi azole-linked compounds were synthesized via a dehydrative cyclization using the Burgess reagent in a single-mode microwave <2003BML3909>. 

Rearrangement under anhydrous conditions serves as an entry to cyclobutenes. The two most commonly employed reagents are TsOH (Eq. 41) and the Burgess reagent [CH302CNS02N(C2H5)3] (Eq. 42), both in refluxing benzene 74). Hydrolysis... 

Methyl (carboxysulfamoyl)triethylammonium hydroxide, inner salt (Burgess reagent). 

Next, the TMS enol ether of 53c underwent oxidation with MCPBA to trimethylsilyloxy ketone 57. in 86% yield (86% conversion). Addition of methylmagnesium bromide in methylene chloride proceeded in almost quantitative yield (95%) to give tertiary alcohol 58. Dehydration with Burgess reagent [19] and acidic workup provided the allylic alcohol 59a in 63% yield, which was converted... 

Tab. 5.4 Cyclodehydration of hydroxyamides and thioamides with polymeric Burgess reagent 26.

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