Michael addition of sulfur

Table I. Pseudo first-order rate constants for Michael addition of sulfur Nucleophiles (5 mM) to aciylic acid and acrylonitrile in seawater medium (salinity 35 and reaction pH 8.3 0.2)...

Thomas, B. E., Kollman, P. A. An ab initio molecular orbital study of the first step of the catalytic mechanism of thymidylate synthase the Michael addition of sulfur and oxygen nucleophiles. J. Org. Chem. 1995, 60, 8375-8381. 

Table 5.9. Asymmetric Michael additions of sulfur and phosphorous stabilized allyllithiums. The X column refers to the auxiliaries in Figure 5.10.

Table 2.17 Hetero Michael addition of sulfur nucleophiles...

The Michael addition of sulfur ylides to nittoalkenes, catalysed by various thioureas, has been studied theoretically. ... 

A range of L-cysteine derivatives bearing a 1,2,4-triazolyl residue on the sulfur atom has been prepared by the asymmetric Michael addition of 4,5-dialkyl-3-mercapto-l,2,4-triazoles to a nickel Schiff base complex. The enantiomeric excesses of the product aminoacids were measured and found to be greater than 98.5% in some cases <2004TA705, 2004RCB932, 2004IZV894>. 

Nitronates (5) can be synthesized by the Michael addition of in situ generated sulfur or selenium ylides (12) (58-60, 62, 63) to conjugated nitroalkenes... 

Stereoselective Michael additions of carbon-, nitrogen-, oxygen-, and sulfur-centered nucleophiles to 6,7-dehydro-5-oxoindolizidine have been reported <2006JOC6630>. 

Application of an organocatalytic domino Michael addition/intramolecular aldol condensation to the preparation of a series of important heterocycles has recently received much attention [158] with methods being disclosed for the preparation of benzopyrans [159-161], thiochromenes [162-164] and dihydroquinolidines [165, 166]. The reports all use similar conditions and the independent discovery of each of these reactions shows the robust nature of the central concept. A generalised catalytic cycle which defines the principles of these reports is outlined in Fig. 10. Formation of iminium ion 102 is followed by an intermolecular Michael addition of an oxygen, sulfur or nitrogen based nucleophile (103) to give an intermediate... 

Dibenzofuranols are available by Michael addition of l-morpholino-1-cyclohexenes (198) to 1,4-benzoquinones (197, Scheme 50). Treatment of the intermediate adducts 199 with acid affords 6,7,8,9-tetrahydro-2-dibenzofuranols (200), which on dehydrogenation with sulfur or palladized charcoal afford the dibenzofuranols 201 in good yield. 

The last topic in this chapter is the Michael addition of heteroatoms such as nitrogen and sulfur that affords P-aminocarbonyl and [Lthiocarbonyl compounds. 

Teyssot et al. reported that the Michael addition of bis(nitrogen or sulfur) nucleophiles to divinyl sulfone provided the corresponding macrocyclic adducts in good yields <2003EJ054>. For example, 9 and 10 have been prepared in 82% and 80% yields, by the reaction of divinyl sulfone with bis(2-mercaptoethyl)ether and 4,7-dioxa-l,10-dithiade-cane, respectively. The X-ray structure of 10 was also reported. 

Michael additions of organolithium, Grignard, and diorganozinc reagents to enones and other rt, -unsaturated carbonyl compounds are catalyzed inter alia by copper, nickel and cobalt salts. The best results are obtained with cop-per(I) catalysts, especially those in which copper is bound to a soft , readily polarizable center (sulfur or phosphorus). 

Formation of three-membered-ring systems can also be the result of a nucleophilic addition leading to a zwitterionic intermediate, followed by loss of nitrogen. In these cases, the reactions are related to the addition of sulfur or phosphorus ylides to Michael acceptors. ... 

Instead of preparing the sulfoxide chirophore via a separation of diastereoisomers, the dia-stereoselective oxidation of a sulfide offers an interesting alternative. Thus Michael addition of 10-mer-captoisobomeol (414) to methyl propiolate furnished (Z)-vinyl sulfide (415) which underwent a hydroxy-directed oxidation (MCPBA) to give the (sulfur-R)-vinyl sulfoxide (416) in a highly selective manner (Scheme 100). ... 

Michael addition of alcohols, thiols and amides expectedly gave high yields with all three sulfur derivatives 2-4 of trifluoropropene and interestingly the sulfoxide 2 furnished with thiophenol beyond the expected monoaddition the dithioacetal of trifluoropropanal (Scheme 21). 

As will be discussed in the next section, 1,5-pentanediones are obtained by Michael addition of acetophenones to chalcones. The addition and cyclization may be merged in one step (see Section II,C,2,g). When acetophenone was condensed with chalcone (74) in the presence of BFg-EtaO or of HC104, jS-phenylpropio-phenone (76) was obtained as by-product its formation is due to hydride transfer to the conjugate acid of chalcone (75), which is the acceptor (experimental data and theoretical calculations show that chalcones are protonated at the oxygen atom). Balaban obtained a 72% yield in the conversion 70 -> 37 using as acceptor chalcone and as catalysts perchloric or sulfuric acids (i.e., 75). The formation of j8-phenylpropiophenone (76) in the Chichibabin synthesis of pyridines from chalcones and ketones in the presence of ammonium acetate, and in the pyrimidine synthesis from chalcones and amidines is undoubtedly due to a similar hydride transfer. 

S-Alkylation by a Michael addition of the thiono sulfur to a-bromoacrylic acid gives an intermediate... 

An alternative process, always involving the formation of an activated electrophile, is adopted by propar-gylglycine, a well-known inhibitor of PLP-dependent enzymes involved in the trans-sulfuration pathways. The mechanism used by proparglycine to inhibit CGS, CGL," and MGL involves the attack of PLP and the formation of an allene intermediate, subsequently transformed into a stable ketimine derivative, by the Michael addition of an enzyme nucleophile residue (Figure 32). 

A reliable one step synthesis of 4-aryl-2,6-diphenylpyrylium salts involves heating benzaldehydes with acetophenone in the presence of either sulfuric or perchloric acid (94OPP101). 2-Amino-3-aroyl-diarylpyrylium salts result from the cyclisation of S-ketonitriles derived from the Michael addition of aroylacetonitriles to chalcones (94JPR623). 

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