Sulfoxides, vinyl ketones

Methyl phenyl sulfide, see Thioanisole Methyl phenyl sulfoxide, 46, 78 from methylsulfinyl chloride and benzene with anhydrous alumi num chloride, 46, 80 Methyl vinyl ketone, reaction with 1-morpholino 1 cyclohexene, 45,... 

For the addition of ethylene, EtOAc as solvent was particularly advantageous and gave 418 in 60% yield (Scheme 6.86). The monosubstituted ethylenes 1-hexene, vinylcyclohexane, allyltrimethylsilane, allyl alcohol, ethyl vinyl ether, vinyl acetate and N-vinyl-2-pyrrolidone furnished [2 + 2]-cycloadducts of the type 419 in yields of 54—100%. Mixtures of [2 + 2]-cycloadducts of the types 419 and 420 were formed with vinylcyclopropane, styrene and derivatives substituted at the phenyl group, acrylonitrile, methyl acrylate and phenyl vinyl thioether (yields of 56-76%), in which the diastereomers 419 predominated up to a ratio of 2.5 1 except in the case of the styrenes, where this ratio was 1 1. The Hammett p value for the addition of the styrenes to 417 turned out to be -0.54, suggesting that there is little charge separation in the transition state [155]. In the case of 6, the p value was determined as +0.79 (see Section 6.3.1) and indicates a slight polarization in the opposite direction. This astounding variety of substrates for 417 is contrasted by only a few monosubstituted ethylenes whose addition products with 417 could not be observed or were formed in only small amounts phenyl vinyl ether, vinyl bromide, (perfluorobutyl)-ethylene, phenyl vinyl sulfoxide and sulfone, methyl vinyl ketone and the vinylpyri-dines. 

Methyl vinyl ketone, see 2-Methyl-l, 3-butadiene Molinate sulfoxide, see Molinate Monobutyl phosphate, see Tributyl phosphate Monobutyl phthalate, see Benzyl butyl phthalate Mono-n-butyl phthalate, see Di-n-butyl phthalate Monobutyl phthalate, see Di-n-butyl phthalate Monochlorobenzidine, see 3,3 -Dichlorobenzidine Monochlorobiphenyl, see Chlorobenzene, PCB-1221, PCB-1254... 

Stereochemistry of this reaction is also quite interesting. Thus, both geometrical isomers of 1-chlorovinyl p-tolyl sulfoxides (165-167) were synthesized from 2-cyclohexenone, methyl vinyl ketone and 2-heptanone respectively, and the corresponding magnesium alkylidene carbenoids were generated and treated with A-lithio aniline or A-lithio 1-aminonaphthalene. The results are summarized in Table 9. 

Phenolannelation. Methyl vinyl ketone (and substituted vinyl ketones) undergo Robinson annelation with the /(-keto sulfoxide (1) to afford the 5,6,7,8-tetrahydro-2-naphthol (2) with loss of hcn/cnesnlfenic acid. Sodium methoxide is used as base, and the reaction proceeds at 0 - 25°. 

The use of a-thiophenyl enones (106 Scheme 12) allows the preparation of phenols such as (107) from cyclic ketones (18).30 The same product can also be obtained by normal Robinson annulation of methyl vinyl ketone (30) and the p-keto sulfoxide (lOS).30 Acceptors other than a, 3-unsaturated carbonyls have been used in both the Michael reaction and the Robinson annulation process. For example, nu-... 

Vinyl ketone equivalent cf., 5, 525-526). y-Keto sulfoxides such as 1 can function as equivalents to vinyl ketones. Thus 1 reacts with dimedone in the presence of triethylaraine (1.5equiv.) in refluxing CH3OH to give the Michael adduct 2 in 79% yield. ... 

This behavior of the RS-C=C fragment may be inverted by properly handling sulfur polarity. Thus, its oxidation to a vinyl sulfoxide converts this unit into an excellent two-carbon Michael acceptor —notice that methyl vinyl ketone and its many equivalents are all three-carbon acceptors. This ambivalent polarizability by simple synthetic operations makes organosulfur synthons very interesting. 

But-2-enedinitrile, 2-nitropropene, phenyl vinyl sulfoxide, styrene and but-2-enal do not form 1-methoxy-l -phenylcyclopropanes with the corresponding chromium-carbene complex. " On the other hand, methyl vinyl ketone gave a formal 1,4-adduct, which, due to its instability, was further transformed under acidic conditions. ... 

A versatile non-Friedel-Crafts approach to naphthols is provided by condensation of the toluic acid sulfoxide with substituted acrylates or methyl vinyl ketone. Sequential conjugate addition and acylation of the first formed anion leads to the tetralone. Pyrolysis leads to aromatiza-tlon by loss of sulfinic acid. 

In a paper published along with that of Stevens and Wentland20 and in agreement with these authors, Keely and Tahk23 reported the independent synthesis of dl-mesembrine, also from I-methyl-3-(3,4-dimethoxyphenyl)-2-pyrroline and methyl vinyl ketone. In their work the cyclopropyl derivative 3b was prepared from the reaction of the anion of 3,4-dimethoxyphenylacetonitrile (lc) with ethylene dibromide in dimethyl sulfoxide and its sodium salt as solvent and base. Reduction with ethereal diisobutylaluminum hydride gave the aldehyde, which was condensed with excess methylamine in benzene-ether solution with calcium oxide as the dehydrating agent. 

Zard has studied the isomerization/Mislow-Evans rearrangement of vinyl sulfoxides such as 237, arising from enolate addition to alkynyl sulfoxides [Scheme 18.60). Isomerization of 237 to the allylic sulfoxide 238 enabled the [2,3]-sigmatropic rearrangement to a-hydroxy-a-vinyl ketone 239. In this case, diastereoselectivity was low in formation of the carbinol center within a steroid framework. Additions to allenyl sulfoxides provide a similar sequence, leading to 2-propenyl substitution at the tertiary alcohol center (not shown). 

The energetic driving force for conjugate addition is the replacement of a tt bond by a cr bond. Among Michael acceptors that have been demonstrated to react with ketone and ester enolates under kinetic conditions are methyl a-trimethylsilyl-vinyl ketone/ methyl a-methylthioacrylate/ methyl methylthiovinyl sulfoxide, and ethyl a-cyanoacrylate. The latter class of acceptors has been shown to be capable of generating contiguous quaternary carbon centers. 

Vinyl Pyrroles. Relatively new synthetic routes based on a one-pot reaction between ketoximes and acetjiene ia an alkaU metal hydroxide—dimethyl sulfoxide (DMSO) system have made vinyl pyrroles accessible. It requires no pyrrole precursors and uses cheap and readily available ketones (42). 

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