Michael/amination

One of the first attempts in this field refers to a multicomponent intermolecular sulfa-Michael/amination cascade process in which an a,p-unsatu-rated aldehyde and a thiol were reacted in the presence of a dialkyl azodicarboxylate reagent, giving access to p-amino-y-thioalcohol derivatives with excellent yields and enantioselectivities. Isolation of the final products was accomplished by in situ reduction followed by base-promoted cyclization (Scheme 7.48). 0-Trimethylsilyl diarylprolinol 31c was identified as the best... 

SCHEME 14.14. Sulfa-Michael addition to a. -unsaturated aldehydes promoted by O-protected diarylprolinol 17a, and related sulfa-Michael-amination cascade process. 

SCHEME 14.19. Sulfa-Michael amination tandem process with a,p-disubstituted enals promoted by the TFA salt of 21. 

SCHEME 16.2. Three-component Michael/amination sequence. 

Scheme 4.32 Carba-Michael/amination cascade reaction.

Scheme 42.10 Organocatalytic domino sulfa-Michael/amination process by way of an iminium ion-enamine sequence both catalytic steps are intermolecular reactions. Protocol point compound 34 was added after 30 min.

Scheme 42.14 Organocatalytic MCRs of a-branched a,p-unsaturated aldehyde enals by way of an iminium ion/enamine sequence Friedel-Crafts/amination strategy and sulfa-Michael/ amination strategy. Protocol point all substrates added at the outset of the reaction.

In the above reaction one molecular proportion of sodium ethoxide is employed this is Michael s original method for conducting the reaction, which is reversible and particularly so under these conditions, and in certain circumstances may lead to apparently abnormal results. With smaller amounts of sodium alkoxide (1/5 mol or so the so-called catal3rtic method) or in the presence of secondary amines, the equilibrium is usually more on the side of the adduct, and good yields of adducts are frequently obtained. An example of the Michael addition of the latter type is to be found in the formation of ethyl propane-1 1 3 3 tetracarboxylate (II) from formaldehyde and ethyl malonate in the presence of diethylamine. Ethyl methylene-malonate (I) is formed intermediately by the simple Knoevenagel reaction and this Is followed by the Michael addition. Acid hydrolysis of (II) gives glutaric acid (III). 

Progress has been made toward enantioselective and highly regioselective Michael type alkylations of 2-cyclohexen-l -one using alkylcuprates with chiral auxiliary ligands, e. g., anions of either enantiomer of N-[2-(dimethylamino)ethyl]ephedrine (E. J. Corey, 1986), of (S)-2-(methoxymethyl)pyrrolidine (from L-proline R. K. EHeter, 1987) or of chiramt (= (R,R)-N-(l-phenylethyl)-7-[(l-phenylethyl)iinino]-l,3,5-cycloheptatrien-l-amine, a chiral aminotro-ponimine G. M. Villacorta, 1988). Enantioselectivities of up to 95% have been reported. 

Primary and secondary amines also react with epoxides (or in situ produced episulfides )r aziridines)to /J-hydroxyamines (or /J-mercaptoamines or 1,2-diamines). The Michael type iddition of amines to activated C—C double bonds is also a useful synthetic reaction. Rnally unines react readily with. carbonyl compounds to form imines and enamines and with carbo-tylic acid chlorides or esters to give amides which can be reduced to amines with LiAlH (p. Ilf.). All these reactions are often applied in synthesis to produce polycyclic alkaloids with itrogen bridgeheads (J.W. Huffman, 1967) G. Stork, 1963 S.S. Klioze, 1975). 

Michael condensations are catalyzed by alkaU alkoxides, tertiary amines, and quaternary bases and salts. Active methylene compounds and aUphatic nitro compounds add to form P-substituted propionates. These addition reactions are frequendy reversible at high temperatures. Exceptions are the tertiary nitro adducts which are converted to olefins at elevated temperatures (24). 

Other reactions that show preference for the acidic N-3—H group include Mannich aminomethylation by treatment with formaldehyde and an amine (38) to yield compound (8), reaction with ethyleneimine (39) to give (9), and Michael-type additions (40) such as the one with acrylonitrile to give (10) ... 

This Michael-type addition is catalyzed by lanthanum(3+) [16096-89-2] (80). Ethylene glycol [107-21-1] reacts with maleate under similar conditions (81). A wide range of nucleophilic reagents add to the maleate and fumarate frameworks including alcohols, ammonia, amines, sulfinic acids, thioureas, Grignard reagents, Michael reagents, and alkali cyanides (25). 

Primary cycloaUphatic amines react with phosgene to form isocyanates. Reaction of isocyanates with primary and secondary amines forms ureas. Dehydration of ureas or dehydrosulfuri2ation of thioureas results in carhodiimides. The nucleophilicity that deterrnines rapid amine reactivity with acid chlorides and isocyanates also promotes epoxide ring opening to form hydroxyalkyl- and dihydroxyalkylaniines. Michael addition to acrylonitrile yields stable cyanoethylcycloalkylarnines. 

Primary fatty amines also add (Michael addition) to esters of acryUc acid, H2C=CHCOOH, methacrylic acid, H2C=C(CH2)COOH, or crotonic acid, CH2CH=CHC00H. Hydrolysis of the Michael ester forms an amphoteric surfactant. Crotonic acid can be used to form the amphoteric compound... 

The Michael addition reaction of amines and thiols with bismaleimides or functionalized monomaleimides is a versatile tool ia the synthesis of chain-extended maleimide-terroinated prepolymers. These prepolymers generally are soluble ia organic solvents from which they can be processed to prepreg and molded to high quaUty, void-free laminates. 

N-Unsubstituted pyrazoles and imidazoles add to unsaturated compounds in Michael reactions, for example acetylenecarboxylic esters and acrylonitrile readily form the expected addition products. Styrene oxide gives rise, for example, to 1-styrylimidazoles (76JCS(P1)545). Benzimidazole reacts with formaldehyde and secondary amines in the Mannich reaction to give 1-aminomethyl products. 

Purines, N-alkyl-N-phenyl-synthesis, 5, 576 Purines, alkylthio-hydrolysis, 5, 560 Mannich reaction, 5, 536 Michael addition reactions, 5, 536 Purines, S-alkylthio-hydrolysis, 5, 560 Purines, amino-alkylation, 5, 530, 551 IR spectra, 5, 518 reactions, 5, 551-553 with diazonium ions, 5, 538 reduction, 5, 541 UV spectra, 5, 517 Purines, N-amino-synthesis, 5, 595 Purines, aminohydroxy-hydrogenation, 5, 555 reactions, 5, 555 Purines, aminooxo-reactions, 5, 557 thiation, 5, 557 Purines, bromo-synthesis, 5, 557 Purines, chloro-synthesis, 5, 573 Purines, cyano-reactions, 5, 550 Purines, dialkoxy-rearrangement, 5, 558 Purines, diazoreactions, 5, 96 Purines, dioxo-alkylation, 5, 532 Purines, N-glycosyl-, 5, 536 Purines, halo-N-alkylation, 5, 529 hydrogenolysis, 5, 562 reactions, 5, 561-562, 564 with alkoxides, 5, 563 synthesis, 5, 556 Purines, hydrazino-reactions, 5, 553 Purines, hydroxyamino-reactions, 5, 556 Purines, 8-lithiotrimethylsilyl-nucleosides alkylation, 5, 537 Purines, N-methyl-magnetic circular dichroism, 5, 523 Purines, methylthio-bromination, 5, 559 Purines, nitro-reactions, 5, 550, 551 Purines, oxo-alkylation, 5, 532 amination, 5, 557 dipole moments, 5, 522 H NMR, 5, 512 pJfa, 5, 524 reactions, 5, 556-557 with diazonium ions, 5, 538 reduction, 5, 541 thiation, 5, 557 Purines, oxohydro-IR spectra, 5, 518 Purines, selenoxo-synthesis, 5, 597 Purines, thio-acylation, 5, 559 alkylation, 5, 559 Purines, thioxo-acetylation, 5, 559... 

In contrast, tertiary amines do not possess a proton to transfer, and the reaction of the Michael-type addition adduct with ECA can only initiate polymerization to form high molecular weight adhesive polymer, as shown earlier in Scheme 1. 

The Bsmoc derivative is formed from the chloroformate or the A -hydroxy-succinimide ester. It is cleaved rapidly by a Michael addition with tris(2-aminoethyl)amine at a rate that leaves Fmoc derivatives intact. More hindered bases, such as A -methylcyclohexylamine or diisopropylamine, do not react with the Bsmoc group, but do cleave the Fmoc group, illustrating the importance of steric effects in additions to Michael acceptors. 

These amines gave, with methyl propiolate, products of Michael mono- and bis-addition. Adducts underwent further reaction leading to triazolo[4,5-/]quinolones 181, after retro Diels-Alder reaction and acetylene elimination to its methoxycar-... 

Addition of p-tert-butylthiophenol 178 to the racemic furanone 168 in dry toluene, and in the presence of quinidine as a chiral catalyst, provided (/ )-168 together with the Michael adduct 179. The enantiomeric excess of the recovered furanone (R)-168 was determined via the addition of (/)-Q -methylbenzylamine This amine addition showed complete diastereofacial control to give the adduct 180 in quantitative yield (Scheme 50) (94T4775). 

Methyl vinyl ketone 2 tends to polymerize, especially in the presence of a strong base the yield of annulation product is therefore often low. A methyl vinyl ketone precursor, e.g. 6, is often employed, from which the Michael acceptor 2 is generated in situ, upon treatment with a base. The quaternary ammonium salt 6 can be obtained by reaction of the tertiary amine 5, which in turn is prepared from acetone, formaldehyde and diethylamine in a Mannich reaction. 

Since most often the selective formation of just one stereoisomer is desired, it is of great importance to develop highly selective methods. For example the second step, the aldol reaction, can be carried out in the presence of a chiral auxiliary—e.g. a chiral base—to yield a product with high enantiomeric excess. This has been demonstrated for example for the reaction of 2-methylcyclopenta-1,3-dione with methyl vinyl ketone in the presence of a chiral amine or a-amino acid. By using either enantiomer of the amino acid proline—i.e. (S)-(-)-proline or (/ )-(+)-proline—as chiral auxiliary, either enantiomer of the annulation product 7a-methyl-5,6,7,7a-tetrahydroindan-l,5-dione could be obtained with high enantiomeric excess. a-Substituted ketones, e.g. 2-methylcyclohexanone 9, usually add with the higher substituted a-carbon to the Michael acceptor ... 

Aldol condensation of the methoxymethyl ether of m-methoxybenzaldehyde (83) with cyclohexanone affords the conjugated ketone 84. Michael addition of dimethyl amine leads to the ami noketone Reduction of the ketone... 

---