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Organoselenium chemistry II. A method for the protection of α-methylene lactones

✍ Scribed by Paul A. Grieco; Masaaki Miyashita

Book ID
104244273
Publisher
Elsevier Science
Year
1974
Tongue
French
Weight
155 KB
Volume
15
Category
Article
ISSN
0040-4039

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✦ Synopsis

The use of protecting groups which prevent Michael-type additions of nucleophilic reagents to the reactive sites of CY-methylene lactones has received little attention. lhe need to effect protection of an ol-methylene lactone function as a result of work in our laboratories involving the synthesis of complex molecules possessing a-methylene lactone moieties, has led to a search for a mild and potentially useful new blocking sequence. It has been reported that dimethylamine* 3 and thiols undergo a reversible addition to conjugated a-methylene la&ones. The removal of these protecting groups involves conversion to their corresponding methiodides and subsequent treatment with saturated aqueous sodium bicarbonate solution. 394 We wish to report a new blocking sequence for the protection of highly reactive conjugated a-methylene la&ones.

Our approach employs a) a Michael-type addition of phenyl selenium anion to the a-methylene la&one and b) a "retro-Michael" reaction via the corresponding selenoxide which reestablishes the a-methylene unit. The method is based on the observations by Sharpless and Jones6 that

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