Polymerization of oxazolines

Diels-Alder cycloadditions of 2-pyrones and 2-pyridones

Natural and synthetic 2H-pyran-2-ones and their versatility in organic synthesis☆

Alkyl and aryl phosphites and phosphines react with compounds having weak heteroatom–heteroatom bonds, such as SS, OO, etc., and with azo compounds to form reactive phosphonium salts. These phosphonium salts in turn promote “redox” condensation reactions with compounds having active hydrogens. The condensation reaction of alcohols using the redox couple of a triaryl- or trialkylphosphine and a dialkyl azodicarboxylate has become known as the Mitsunobu reaction, based on his pioneering work in the late 1960s. The overall reaction is summarized, wherein the alcohol (R1OH) and acidic compound (H–Nu) are condensed to form product (R1–Nu), while triphenylphosphine is oxidized to triphenylphosphine oxide and the azodicarboxylate is reduced to the hydrazine. Although the typical redox combination is diethyl azodicarboxylate (DEAD) and triphenylphosphine, many other combinations have found selected use. The reaction is generally limited to primary and secondary alcohols, although tertiary alcohols react in a few intramolecular and intermolecular reactions. For secondary alcohols the reaction usually proceeds with clean inversion of stereochemistry. The acidic component of the reaction generally has an aqueous pKa < 15, with intramolecular reactions providing the exceptions. Examples of H–Nu include oxygen nucleophiles such as carboxylic acids and phenols; nitrogen nucleophiles such as imides, hydroxamates, and heterocycles; sulfur nucleophiles such as thiols and thioamides; and carbon nucleophiles such as β-ketoesters.



Major reviews of the Mitsunobu reaction were published in 1981 by Mitsunobu and in 1983 by Castro. The former review concentrated on reactions using DEAD/triphenylphosphine, while the latter review focused on reactions in which halogens replaced the hydroxy group using reagents such as triphenylphosphine/carbon tetrachloride, triphenyl phosphite/iodomethane, and triphenylphosphine/N-halosuccinimide. Reactions involving the DEAD/triphenylphosphine redox system are the principal subject of this chapter, with emphasis on the literature between 1981 and 1988.


Keywords:

Mitsunobu reaction;
adduct formation;
alcohol activation;
SN2 reaction;
mechanisms;
carbon–oxygen bond;
carbon–nitrogen bond;
carbon–sulfur bond;
carbon–halogen bond;
carbon–carbon bond;
ambident nucleophiles;
dehydration;
alkenes;
method comparison;
ester formation;
lactone formation;
akyl aryl ether;
epoxides;
dialkyl ethers;
enol ethers;
dialkyl ethers;
imides;
azides;
experimental procedures;
scope;
limitations

The Mitsunobu Reaction

Certain substituted urea derivatives selectively modulate the cardiac sarcomere, for example by potentiating cardiac myosin, and are useful in the treatment of systolic heart failure including congestive heart failure.

Certain chemical entities, compositions and methods

A Mild Procedure for the Preparation of 2-Oxazolines

Oxazole and thiazole compounds of the following formula are photodynamic insecticides and acaricides as well as nematicides: ##STR1## wherein W is selected from O and S; R 2 is selected from optionally substituted thienyl and optionally substituted phenyl; R 4 is selected from hydrogen, lower alkyl, lower haloalkyl, thienyl, tri(lower alkyl)silyl, and optionally substituted phenyl; R 5 is selected from optionally substituted thienyl and optionally substituted phenyl; at least one of R 2 and R 5 is an optionally substituted thienyl group, and R 4 is other than hydrogen when R 4 and R 5 are each unsubstituted phenyl or thienyl.

Photoactive azole pesticides

Selon l'enamine choisie, obtention soit des alkyl-3 ou -4 dimethyl-2,6 benzoates d'ethyle, soit des alkyl-3 dimethyl-2,6 morpholino-4 cyclohexadiene-1,5 carboxylates d'ethyle

Inverse electron demand Diels-Alder reactions of 4,6-dimethyl-2-oxo-2H-pyran-5-carboxylic acid esters and morpholino enamines: regiospecific preparation of 3- or 4-substituted-2,6-dimethylbenzoates

Des composes de bithienyle sont des insecticides et acaricides phototoxiques, et ont la formule structurale suivante (I) ou R1 est selectionne parmi l'hydrogene, un halogene, alkyle, haloalkyle, alkoxy, haloalkoxy, haloalkenoxy, phenyle, phenoxy, nitro, alkylsulfinyle, alkylsulfonyle, et alkylthio a condition que R4 soit different de l'hydrogene; Compounds bithienyl are phototoxic insecticides and acaricides, and have the following structural formula (I) wherein R1 is selected from hydrogen, halogen, alkyl, haloalkyl, alkoxy, haloalkoxy, haloalkenoxy, phenyl, phenoxy, nitro, alkylsulfinyl, alkylsulfonyl, and alkylthio provided that R4 is different from hydrogen; R2 est selectionne parmi l'hydrogene et un halogene, ou bien R1 et R2 en positions adjacentes sont reunis pour former C4H4; R2 is selected from hydrogen, halogen, or R1 and R2 in adjacent positions together to form C4H4; R3 est selectionne parmi l'hydrogene, un alkyle, thienyle, et un phenyle eventuellement substitue avec de l'alkyle, alkoy, ou 1 a 2 halogene; R3 is selected from hydrogen, alkyl, thienyl, and phenyl optionally substituted with alkyl, alkoy, or 1 to 2 halogen; et R4 est selectionne parmi l'hydrogene, un halogene, alkyle, haloalkyle, alkoxy, alkylthio, alkylsulfinyle, haloalkenylthio, formyle, alkylcarbonyle, alkoxycarbonyle, phenylcarbonyle, dialkylphosphono, et nitro. and R4 is selected from hydrogen, halogen, alkyl, haloalkyl, alkoxy, alkylthio, alkylsulfinyl, haloalkenylthio, formyl, alkylcarbonyl, alkoxycarbonyl, phenylcarbonyl, dialkylphosphono, and nitro.

Photoactive bithienyl pesticides

Thiophene derivatives of the following formula are effective as acaricdies: ##STR1## wherein A is selected from -phenylthienyl and -phenyl optionally carrying one or more substitutents selected from -lower alkyl, -lower alkoxy, -phenoxy, -hydroxy, -halogen, -lower haloalkyl, -phenylcarbonyl, -lower alkyl carbonyloxy, -lower alkyl sulfonyl, -lower alkyl sulfonyloxy, -amino, -lowr alkyl carboxamido, and -lower haloalkyl carboxamido; R4 is selected from -hydrogen and -lower alkyl; and R5 is selected from -thienyl optionally carrying one or more substituents selected from -lower alkyl, -phenylethynyl, -lower alkylthio, -lower haloalkyl carbonyl, and lower alkyl sulfoxy; or -phenyl optionally carrying one or more substituents selected from -lower alkyl and -lower alkoxy.

David M. Roush

Papers

A Mild Procedure for the Preparation of 2-Oxazolines

Photoactive azole pesticides

Inverse electron demand Diels-Alder reactions of 4,6-dimethyl-2-oxo-2H-pyran-5-carboxylic acid esters and morpholino enamines: regiospecific preparation of 3- or 4-substituted-2,6-dimethylbenzoates

Photoactive bithienyl pesticides

2-Substituted ethynyl thiophene pesticides