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Topic: Aldol reaction

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Aldol condensation

Condensation reaction

	Aldol reaction - Wikipedia, the free encyclopedia
		If the catalyst is a moderate base such as hydroxide ion or an alkoxide, the aldol reaction occurs via nucleophilic attack by the resonance-stabilized enolate on the carbonyl group of another molecule.
		The aldol reaction may exhibit "substrate-based stereocontrol", in which existing chirality on either reactant influences the sterochemical outcome of the reaction.
		In the syn-selective reactions, both enolization methods give the Z enolate, as expected; however, the stereochemical outcome of the reaction is controlled by the methyl stereocenter, rather than the chirality of the oxazolidinone.
	en.wikipedia.org /wiki/Aldol_reaction (2251 words)

	Carbonyl Reactivity
		A useful carbon-carbon bond-forming reaction known as the Aldol Reaction or the Aldol Condensation is yet another example of electrophilic substitution at the alpha carbon in enols or enolate anions.
		The fundamental transformation in this reaction is a dimerization of an aldehyde (or ketone) to a beta-hydroxy aldehyde (or ketone) by alpha C–H addition of one reactant molecule to the carbonyl group of a second reactant molecule.
		The exception, reaction #3, is conducted under mild conditions with an excess of the reactive aldehyde formaldehyde serving in the role of electrophilic acceptor.
	www.cem.msu.edu /~reusch/VirtualText/aldket2.htm (3411 words)

	Aldol reaction: Encyclopedia topic (Site not responding. Last check: 2007-09-11)
		The aldol reaction is an important organic reaction (organic reaction: more facts about this subject) involving the reaction of enolate ions (enolate ions: enol (or, more officially, but less commonly: alkenol) is an alkene with hydroxyl...
		The reaction is then called a aldol condensation (aldol condensation: an aldol condensation is a organic reaction where a enolate ion reacts with a carbonyl...
		Aldol reactions between two different aldehydes or ketones are generally not successful, as they tend to produce a mixture of different products.
	www.absoluteastronomy.com /reference/aldol_reaction (473 words)

	Aldol reaction: Facts and details from Encyclopedia Topic (Site not responding. Last check: 2007-09-11)
		An aldol condensation is a organic reaction where a enolate ion reacts with a carbonyl compound to form a -hydroxyaldehyde or -hydroxyketone...
		The oxymercuration reaction is a chemical reaction used in organic chemistry to form a neutral alcohol without any rearrangement of carbocations....
		An electrophilic aromatic substitution is a chemical reaction in which a hydrogen atom of an aromatic ring is replaced by an electrophile....
	www.absoluteastronomy.com /encyclopedia/A/Al/Aldol_reaction.htm (911 words)

	Supplemental Topics
		Reaction 4 is an interesting case in which the catalyzed aldol is followed by an acetal exchange involving the new hydroxyl group.
		The stereospecifity of these aldol reactions is improved by using nonpolar solvents, possibly because the structure of the transition state is tightened due to lack of competitive coordination with boron.
		The Mannich reaction is similar to a crossed aldol reaction in that a nucleophilic enol-donor forms a carbon-carbon bond to an electrophilic iminium-acceptor.
	www.cem.msu.edu /~reusch/VirtualText/suppmnt3.htm (4083 words)

	Aldol: Encyclopedia topic (Site not responding. Last check: 2007-09-11)
		An aldol is both an aldehyde (aldehyde: Any of a class of highly reactive chemical compounds; used in making resins and dyes and organic acids) and an alcohol (alcohol: A liquor or brew containing alcohol as the active agent).
		Aldols can be formed in aldol reaction (aldol reaction: A reaction of aldehydes resulting in an aldol) s.
		Acid/base catalysis (catalysis: Acceleration of a chemical reaction induced the presence of material that is chemically unchanged at the end of the reaction) is reversible.
	www.absoluteastronomy.com /reference/aldol (387 words)

	Asymmetric Cross-Aldol Reactions Of Aldehydes: A Formidable Synthetic Challenge (Site not responding. Last check: 2007-09-11)
		The aldol addition reaction is one of the most versatile, effective and general methods for the formation of C-C bonds in modern organic synthesis.
		However, the aldol reaction of aldehydes has some drawbacks, and a general solution to the problem of stereoselective control has not yet found.
		Several problems are associated with aldol reactions of aldehydes due to the fact they suffer from undesired reactions, such as polyaldolisation (secondary additions to the aldehyde products), oligomerisation of the product (propensity of aldehydes to polymerise under metal-catalysed conditions), dehydration of the product and Tishchenko-type processes (Scheme 1).
	www.organic-chemistry.org /Highlights/2005/25June.shtm (1425 words)

	ECHET 96 for Reinhard Neier (4)
		As we had hoped the yield of the crossed aldol reaction using the dimethyl acetal of phthalimido acetone (56) gave a considerably better yield for the aldol reaction.
		We decided to study two ways to improve the crossed aldol reaction: 1) synthesising the pure regioisomers of the silyl enol ethers; 2) replacing the amide function by another protecting group, compatible with the crossed-aldol reaction.
		The reaction conditions for the pyrrole formation are sufficiently mild to allow also the isolation of highly sensitive pyrroles.
	www.unine.ch /chim/echet96/rnei4.html (1567 words)

	Aldol Condensation
		The aldol reaction is an equilibrium, which may lie to the right or to the left depending on circumstances (see below).
		The aldol reaction may occur between two molecules of the same aldehyde or the same ketone, or between different molecules (crossed aldol reaction).
		The aldol reaction may be used intramolecularly to close five- and six-membered rings, like in the Robinson annulation reaction.
	ivan.tubert.org /caos/reactions/aldol.html (449 words)

	Aldol derivatives of 5-phenyl-1,4-benzodiazepin-2-on-N4-oxide; intriguing inertness of N-oxides in aldol reactions (Site not responding. Last check: 2007-09-11)
		Aldol derivatives of 5-phenyl-1,4-benzodiazepin-2-on-N4-oxide; intriguing inertness of N-oxides in aldol reactions
		Aldol reaction of 2 was then monitored by HPLC under conditions that allow identification of benzoin, as the product of dimerization of benzaldehyde catalyzed by the carbanion of 2, and eventual other side-products.
		The reaction mixture was stirred under argon for 20 h at ambient temperature, then reaction solution was extracted with sat.
	www.arkat-usa.org /ark/journal/2003/I14_Stanovnik/BS-681A/681A.asp (1527 words)

	(WO 03/089396) DIRECT, ENANTIOSELECTIVE ALDOL COUPLING OF ALDEHYDES USING CHIRAL ORGANIC CATALYSTS (Site not responding. Last check: 2007-09-11)
		The reaction may be carried out with a single enolizable aldehyde, resulting in dimerization to give a β-hydroxy aldehyde, or trimerization to give a dihydroxy tetrahydropyran.
		The reaction may also conducted with an enolizable aldehyde and a second aldehyde, which may or may not be enolizable, so that the coupling is a cross-aldol reaction in which the a-carbon of the enolizable aldehyde adds to the carbonyl carbon of the second aldehyde in an enantioselective fashion.
		Reaction systems composed of at least one enolizable aldehyde, an optional additional aldehyde, and the nonmetallic chiral organic catalyst are also provided, as are methods of implementing the enantioselective aldol reaction in the synthesis of sugars.
	wipo.int /cgi-pct/guest/getbykey5?KEY=03/89396.031030&ELEMENT_SET=DECL (227 words)

	aldol
		A crossed aldol reaction n is not a synthetically useful one since a mixture of four products result from this reaction.
		Aldol condensation product can be obtained from any aldol reaction if the reaction is carried out at an elevated temperature.
		A dicarbonyl compound where the two carbonyl groups (aldehyde/ketone) are separated by 2-3 carbon atoms, undergo facile intramolecular aldol reactions.
	www.wiu.edu /users/mftkv/Chem332/aldol.html (309 words)

	Reinhard Neier (4) (Site not responding. Last check: 2007-09-11)
		Using deactivated silyl enol ethers like the silylenol ether from 1,3-cyclohexadione (53) the reaction conditions had to be much harsher and still the yield of the pyrrole 54 was disappointingly low.
		We decided to study two ways of improving the crossed aldol reaction: 1) synthesising the pure regioisomers of the silyl enol ethers; 2) replacing the amide function by another protecting group, compatible with the crossed-aldol reaction.
		The reaction conditions for the pyrrole formation are sufficiently mild to allow the isolation of highly sensitive pyrroles.
	www.ch.ic.ac.uk /ectoc/echet96/papers/112/rnei4.html (1535 words)

	Aldol Addition
		'Aldol' is an abbreviation of aldehyde and alcohol.
		When the enolate of an aldehyde or a ketone reacts at the α-carbon with the carbonyl of another molecule under basic or acidic conditions to obtain β-hydroxy aldehyde or ketone, this reaction is called Aldol Reaction.
		Under conditions of kinetic control, the mixed Aldol Addition can be used to prepare adducts that are otherwise difficult to obtain selectively.
	www.organic-chemistry.org /namedreactions/aldol-addition.shtm (232 words)

	The aldol reaction of silyl enol ethers within a micro-reactor (Site not responding. Last check: 2007-09-11)
		Carbanion chemistry is the most common method of C–C bond formation; however the temperature of such reactions governs the stereochemistry of the product.
		The reaction was successfully performed using a variety of other silyl enol ethers and aldehydes, which demonstrates that micro-reactors can be used in the rapid synthesis of combinatorial libraries.
		An example of aldol condensation to prepare ß-hydroxyketone via silyl enol ether formation of cyclohexanone (figure from [7]).
	www.arches.uga.edu /~asmehta/aldol.html (141 words)

	Chapter 18: Aldol condensation of RCHO
		The reaction involves an enolate reacting with another molecule of the aldehyde.
		The simplest aldol reaction is the condensation of ethanal.
		Students often find this reaction difficult, probably because they are intimidated by it.....
	www.chem.ucalgary.ca /courses/351/Carey/Ch18/ch18-3-4.html (268 words)

	Goodman Group Publications
		Enantio- and diastereoselective aldol reactions of achiral ethyl and methyl ketones with aldehydes: the use of enol diisopinocampheylborinates.
		Aldol reactions in polypropionate synthesis: high π-face selectivity of enol borinates from α-chiral methyl and ethyl ketones under substrate control.
		Aldol reactions of methylketones using chiral boron reagents: a reversal in aldehyde enantioface selectivity.
	www-jmg.ch.cam.ac.uk /publications.html (2324 words)

	(WO 01/27145) ANTIBODY CATALYSIS OF ENANTIO- AND DIASTEREO-SELECTIVE ALDOL REACTIONS (Site not responding. Last check: 2007-09-11)
		(WO 01/27145) ANTIBODY CATALYSIS OF ENANTIO- AND DIASTEREO-SELECTIVE ALDOL REACTIONS
		This hapten combines, in a single molecule, structural components employed for reactive immunization with structural components employed for forming a transition state analog of the aldol reaction.
		Characterization of two of these antibodies reveals that they are highly proficient (up to 1000-fold better than any other antibody catalyst) and enantioselective catalysts for aldol and retro-aldol reactions and exhibit enantio- and diastereo- selectivities opposite that of antibody 38C2.
	wipo.int /cgi-pct/guest/getbykey5?KEY=01/27145.010419&ELEMENT_SET=DECL (175 words)

	The Aldol Reaction
		Simple diastereoselection in the lewis acid mediated reactions of enolsilanes with aldehydes.
		Extending the scope of the Evans asymmetric aldol reaction: preparation of anti and "non-Evans" syn aldols
		Extending the scope of the Evans asymmetric aldol reaction:
	library.caltech.edu /collections/rpb/chemistry/AldolReaction.htm (962 words)

	C2131 The Aldol Reaction (Site not responding. Last check: 2007-09-11)
		one of the very important reactions of enolate ions is the formation of a new carbon-carbon bond through an aldol reaction.
		The reaction has the name aldol because the product can have a hydroxyl group and an aldehyde group.
		equilibrium constants for the aldol reaction generally favour the reactants.
	www.mta.ca /~acockshu/c2131aldol.html (516 words)

	Find in a Library: Stereochemical control of polyketides through asymmetric aldol reaction
		Stereochemical control of polyketides through asymmetric aldol reaction
		To find this item in a library, enter a postal code, state, province, or country in the field above.
		WorldCat is provided by OCLC Online Computer Library Center, Inc. on behalf of its member libraries.
	worldcatlibraries.org /wcpa/ow/3cf4d0c57cc63051a19afeb4da09e526.html (76 words)

	Expt. 18.1C: Aldol Reaction (Site not responding. Last check: 2007-09-11)
		You do not need to worry about the yield....just the purity of the compound.
		Determine the identity of the unknown aldehyde from the melting points of the two aldol adducts you and your partner prepared.
		Attach the carbon copies of your notebook pages to the report and turn in to your lab instructor.
	web.uccs.edu /bgaddis/chem338/e18_2.html (138 words)

	The Aldol Reaction To Be Discussed Thursday (Site not responding. Last check: 2007-09-11)
		"The Aldol Reaction: New Twists for a Classic" is the topic for a Spring Student Colloquium in chemistry at Texas A&M. Barry M. Trost of Stanford University will discuss the subject at 4 p.m.
		Thursday (May 24) in Room 2104 Chemistry Building.
		Stimulated by dramatic developments in controlling selectivity, the aldol reaction has become one of the most powerful reactions for construction of complex molecules.
	www.tamu.edu /univrel/aggiedaily/news/stories/01/051801-6.html (65 words)

	Expt. 18.1C: Aldol Reaction
		Determine the purity of the product by doing a percent error.
		Draw the reaction, showing the structure of the product formed in the reaction.
		You should be able to determine the stereochemistry of the product, based upon your extensive knowledge of organic chemistry.
	web.uccs.edu /bgaddis/chem330/c340expt18_2.html (273 words)

	Publications
		British und American patent: "NMR-Measurement Cell and Procedure for Fast Mixing of at least two Reaction Fluids in the NMR Measurement Cell."
		Juan C. Mareque Rivas, Harald Schwalbe, and Stephen J. Lippard, "Inter-chain hydrogen bonding interactions may facilitate translocation of K+ ions across the potassium channel selectivity filter as suggested by synthetic modeling chemistry", Proc.
		Atsushi Abiko, Tadashi Inoue, H. Furuno, William Davies, Christin Fieres, Harald Schwalbe, and Satoru Masamune, "The first doubly borylated enolate as an intermediate of the double aldol reaction", J. Am.
	schwalbe.org.chemie.uni-frankfurt.de /publications.php (3746 words)

	Caltech Library System
		Chemsoc (International Chemistry Societies' Electronic Network) : Chemsoc Timeline (A linear based exploration of key events in the history of science with a particular emphasis on chemistry.)
		Gunther Grethe (MDLI) - Reaction Information Retrieval; an introductory
		Bob Snyder (MDLI) - Solving the Reaction Retrieval Problem
	www.library.caltech.edu /collections/chemistry.htm (2539 words)

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