Science of Synthesis

Cha, J. K., Science of Synthesis, (2005) 21, 365.

α-Alkylsulfanyl, α-arylsulfanyl, and cognate selenium substituents can be easily introduced to amides and carbamates by displacement of suitable leaving groups such as halo, alkoxy, acyloxy, hydroxy, and sulfonyl functionalities (see Sections ‌21.3.1.2.1‌, ‌21.3.2.1.1‌ and ‌21.3.3.1.3‌). Owing to the high nucleophilicity of the sulfur-based nucleophiles, the substitution reaction proceeds smoothly under basic conditions;[‌182‌,‌201‌,‌202‌] for example, 4-acetoxyazetidinone combines with 2-sulfanylethanol to give the hydroxylated sulfide ‌157‌, which reacts with 2,2-dimethoxypropane and boron trifluoride–diethyl ether complex to afford 2,2-dimethyl-3-oxa-6-thia-1-azabicyclo[5.2.0]nonan-9-one (‌158‌),[‌201‌] whereas a reaction with prop-2-enethiol gives the propenyl sulfide ‌159‌ (‌Scheme 46‌).[‌202‌] This approach has been extensively utilized for the preparation and derivatization of β-lactams.[‌118‌–‌120‌,‌165‌,‌183‌] Although enantioselectivity for the addition to the presumed azetidinone intermediate is not high (only 54% ee), treatment of the sulfone ‌160‌ with an excess of benzenethiol in the presence of cinchonidine gives the phenylsulfanylazetidinone ‌161‌ in 96% yield (‌Scheme 46‌).[‌203‌] Relatively mild acidic conditions can also be employed by taking advantage of N-acyliminium ion intermediates;[‌162‌,‌204‌,‌205‌] thus, for example, the alcohol ‌162‌ reacts with benzenethiol in the presence of 4-toluenesulfonic acid to afford the phenyl sulfide ‌163‌ (‌Scheme 46‌).[‌204‌]

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References

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• 8.Meeeee-Meee, (8888) 88/8, 888.
• 8.Meeeee-Meee, (8888) M 8-8, 8888.
• 8.Meeeee-Meee, (8888) M 88-8, 8888.
• 8.Meeeee-Meee, (8888) M 88e8, 888.