Thiophenoxides Michael addition

Protection of a-methylene-y-butyrolactones. Sodium thiophenoxide undergoes Michael addition to a-methylene-7-butyrolactones in nearly quantitative yield. Deblocking involves oxidation of the sulfide to the sulfoxide and thermal elimination of benzenesulfenic acid. The yield in all steps is high. ... 

Cyclopropanes from aj unsaturated carbonyl compounds. This new transformation is illustrated for conversion of cinnamaldehyde into phenylcyclopropane (equation I). The sequence involves Michael addition of sodium thiophenoxide... 

The maleimide group can undergo a variety of chemical reactions, including polymerizations induced by free radicals or anions. Nucleophiles such as primary and secondary amines , as well as thiophenoxides , can react via a classical Michael-type addition mechanism . The maleimide group can also act as a very reactive dienophile and is thns nsed in a variety of Diels-Alder reactions . By varying the natnre of the linkages between the maleimide rings, the physical properties of the bis(maleimide) can be altered. 

A novel entry into 1,2-thiazin-3-ones (203) can be achieved by a base-catalyzed ring expansion of the 1,2-thiazetidine 1,1-dioxide (204). This reaction is initiated by a retro-Michael process leading to the a)S-unsaturated thioester (205), which cyclizes to the thiazinone (206). Thiophenoxide addition to (206) gives the heterocycle (203) in an overall yield of 90% (Scheme 41) <94LA251>. 

A powerful tandem 1,4-addition/cyclization was reported by Danishefsky in the total synthesis of avermectin A,., (15, Scheme 12.2) [53-55]. In the sequence, conjugate addition of thiophenoxide to enal 12 generates an intermediate enolate that is trapped by addition to the resident ketone. Subsequent oxidation of the sulfide in 13 to the corresponding sulfoxide and thermolysis provided the desired oxahydrindene 14 in 76% overall yield [54]. From advanced intermediate 14, only a few steps were required to complete the synthesis of the anthelmintic agent avermectin Aj (15) [54, 55], Fukumoto developed a stereoselective double Michael sequence for the construction of substituted bicyclo[2.2.2]octanes (Scheme 12.3) [56, 57]. The intramolecular transformation was conducted by treatment of 16 with base and afforded 17 as a single isomer in 58% yield. The sequence is no-... 

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