SUPPORT THE WORK

GetWiki

Orthoester

ARTICLE SUBJECTS
aesthetics  →
being  →
complexity  →
database  →
enterprise  →
ethics  →
fiction  →
history  →
internet  →
knowledge  →
language  →
licensing  →
linux  →
logic  →
method  →
news  →
perception  →
philosophy  →
policy  →
purpose  →
religion  →
science  →
sociology  →
software  →
truth  →
unix  →
wiki  →
ARTICLE TYPES
essay  →
feed  →
help  →
system  →
wiki  →
ARTICLE ORIGINS
critical  →
discussion  →
forked  →
imported  →
original  →
Orthoester
[ temporary import ]
please note:
- the content below is remote from Wikipedia
- it has been imported raw for GetWiki
(File:Orthoesters General Formulae V.1.png|thumb|150px|right|The general formula of orthoesters.)In organic chemistry, an orthoester is a functional group containing three alkoxy groups attached to one carbon atom, i.e. with the general formula RC(OR′)3. Orthoesters may be considered as products of exhaustive alkylation of unstable orthocarboxylic acids and it is from these that the name 'ortho ester' is derived. An example is ethyl orthoacetate, CH3C(OCH2CH3)3, more correctly known as 1,1,1-triethoxyethane. Orthoesters are used in organic synthesis as protecting groups for esters.

Synthesis

Orthoesters can be prepared by the Pinner reaction, in which nitriles react with alcohols under acid catalysis:
RCN + 3 R′OH → RC(OR′)3 + NH3

Reactions

Hydrolysis

Orthoesters are readily hydrolyzed in mild aqueous acid to form esters:
RC(OR′)3 + H2O → RCO2R′ + 2 R′OH
For example, trimethyl orthoformate CH(OCH3)3 may be hydrolyzed (under acidic conditions) to methyl formate and methanol;{{Clayden|page=345}} and may be further hydrolyzed (under alkaline conditions) to salts of formic acid and methanol.United States Patent Application 20070049501, Saini; Rajesh K.; and Savery; Karen, March 1, 2007
(File:OrthoesterHydrolysis.png|600px|Hydrolysis of methyl orthoformate to methyl formate)

Johnson–Claisen rearrangement

The Johnson–Claisen rearrangement is the reaction of an allylic alcohol with an orthoester containing a deprotonatable alpha carbon (e.g. triethyl orthoacetate) to give a {{no wrap|γ,δ-unsaturated}} ester.JOURNAL, Johnson, William Summer., Werthemann, Lucius., Bartlett, William R., Brocksom, Timothy J., Li, Tsung-Tee., Faulkner, D. John., Petersen, Michael R., Simple stereoselective version of the Claisen rearrangement leading to trans-trisubstituted olefinic bonds. Synthesis of squalene, Journal of the American Chemical Society, February 1970, 92, 3, 741–743, 10.1021/ja00706a074,
missing image!
- Johnson-Claisen Rearrangement Scheme.png -
The Johnson–Claisen rearrangement


Bodroux–Chichibabin aldehyde synthesis

In the Bodroux–Chichibabin aldehyde synthesis an orthoester reacts with a Grignard reagent to form an aldehyde; this is an example of a formylation reaction.
missing image!
- Bodroux-Chichibabin Aldehyde Synthesis Scheme.png -
Bodroux-Chichibabin aldehyde synthesis


Use

As a protecting group

(File:Obo-group.png|thumb|right|100px|OBO: 4-methyl-2,6,7-trioxa-bicyclo[2.2.2]octan-1-yl)Both trimethylorthoacetate and triethylorthoacetate are commonly used reagents in organic chemistry. Another example is the bicyclic OBO protecting group (4-methyl-2,6,7-trioxa-bicyclo[2.2.2]octan-1-yl) which is formed by the action of (3-methyloxetan-3-yl)methanol on activated carboxylic acids in the presence of Lewis acids and was developed by Elias James Corey. The group is base stable and can be cleaved in two steps under mild conditions, mildly acidic hydrolysis yields the ester of tris(hydroxymethyl)ethane which is then cleaved using e.g. an aqueous carbonate solution.BOOK, Kocieński, Philip J., Protecting groups, 2005, Thieme, Stuttgart, 978-3-13-135603-1, 3.,

In polymer chemistry

In polymer chemistry orthoesters are used in polyorthoesters and in expanding monomers.

See also

References

{{Reflist}}

- content above as imported from Wikipedia
- "Orthoester" does not exist on GetWiki (yet)
- time: 2:24am EDT - Sat, Aug 18 2018
[ this remote article is provided by Wikipedia ]
LATEST EDITS [ see all ]
GETWIKI 09 MAY 2016
GETWIKI 18 OCT 2015
M.R.M. Parrott
Biographies
GETWIKI 20 AUG 2014
GETWIKI 19 AUG 2014
GETWIKI 18 AUG 2014
Wikinfo
Culture
CONNECT