1- Methylthio-2-propanone

In 1974, Gassman et al. reported a general method for the synthesis of indoles. For example, aniline 5 was reacted sequentially with r-BuOCl, methylthio-2-propanone 6 and triethylamine to yield methylthioindole 7 in 69% yield. The Raney-nickel mediated desulfurization of 7 then provided 2-methylindole 8 in 79% yield. The scope and mechanism of the process were discussed in the same report by Gassman and coworkers as well. 

The mechanism of the indolization of aniline 5 with methylthio-2-propanone 6 is illustrated below. Aniline 5 reacts with f-BuOCl to provide A-chloroaniline 9. This chloroaniline 9 reacts with sulfide 6 to yield azasulfonium salt 10. Deprotonation of the carbon atom adjacent to the sulfur provides the ylide 11. Intramolecular attack of the nucleophilic portion of the ylide 11 in a Sommelet-Hauser type rearrangement produces 12. Proton transfer and re-aromatization leads to 13 after which intramolecular addition of the amine to the carbonyl function generates the carbinolamine 14. Dehydration of 14 by prototropic rearrangement eventually furnishes the indole 8. 

A. Methylthio 2-propanone [2-Propanone, l-methylthio-].2 A 2-1., three-necked, round-bottomed flask is equipped with a sealed mechanical stirrer and a two-necked adapter holding a thermometer and a... 

Propanone, 1-chloro- [78-95-5], 73 2-Propanone, l-chloro-1,1,3,3,3 penta fluoro- [79-53-8], 124 2-Propanone, l-(methylthio) [14109-72... 

Methoxy-a-(phenylthio) ketones, e.g., 3-methoxy-l-phenyl-2-phenylthiopropanone and 5-methoxy-l-phenyl-4-phenylthio-l-penten-3-onc (Table 6), can also be reduced with syn selectivity by zinc borohydride. calcium borohydride and lithium triethylborohydride82. For zinc and calcium borohydride, at least, it is reasonable to suppose that the transition state 4 (where R3 = MOM) is reinforced by /1-chclation. These reagents are actually more successful than L-Selectride in the reduction of 3-methoxy-1-phenyl-2-phenylthiopropanone, where the L-Se-lectridc result is anomalously poor. A /5-hydroxy substrate, 3-hydroxy-2-mcthylthio-l-phenyI-propanone, could be reduced to 2-methylthio-l-phenyl-l,2-propanediol with good syn selectivity using zinc borohydride (yield 65% d.r. 93 7)81. 

Methyl-1 - [4-(methylthio)phenyl] -2-(4-morpholinyl)-1 -propanone (photo iiutiator), 543... 

Greatcure 907. See 2-Methyl-1-[4-(methylthio) phenyl]-2-morpholinopropan-1-one Greatcure 907F. See 1-(4-Fluorophenyl)-2-methyl-2-morpholino-1-propanone Greatcure 1173. See 2-Hydroxy 2-methyl 1-... 

In 1974, Paul Gassman and co-workers recognized the potential of the described rearrangement and reported a one-pot, general method for the synthesis of indoles based on the rearrangement of the nonisolable aza-sulfonium ylides. In the very first example of this method, aniline 4 was treated sequentially with f-BuOCl, methylthio-2-propanone 5 and triethylamine to provide methylthioindole 6 in 69% yield. Raney-nickel-mediated desulfuriza-tion afforded 2-methylindole 7 in 79% yield. 

Mercapto-2-propanone, M-60028 (Methylthio)acetaldehyde, in M-80017 (Methylthio)oxirane, M-80173 Propenylsulfenic acid, P-70123... 

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