Grignard reagents cyclopropyl

I.2.6. Photochemical Cyclization of Allyl Grignard Reagents to Cyclopropyl Grignard Reagents... 

Sulfonyl Azo Compounds. Aryl and cyclopropyl Grignard reagents add to ArN=NTs to give diaryl or cyclopropylarylamines after allylation and reduction (Eq. 22).255 For a similar reaction involving organozinc reagents see Eq. 38. 

Bromo-l-propenyl phenyl sulfone (104) can serve as a Michael acceptor to Grignard reagents to give cyclopropyl phenyl sulfones in good yields, (equation 85)70. Cyclopropanes prepared by this method are listed in Table 8. However, with methyl, ethyl or t-butyl... 

Grignard reagents, no detectable amount of cyclopropyl sulfones is formed. 

TABLE 8. Preparation of cyclopropyl sulfones from 104 and Grignard reagents ... 

This reaction is extended to the intramolecular ring closure of the intermediate radical 224 with olefinic or trimethylsilylacetylenic side chains [121]. Cu(BF4)2 is also effective as an oxidant (Scheme 89) [122]. Conjugate addition of Grignard reagents to 2-eyclopenten-l-one followed by cyclopropanation of the resulting silyl enol ethers gives the substituted cyclopropyl silyl ethers, which are oxidized to 4-substituted-2-cyclohexen-l-ones according to the above-mentioned method [123]. (Scheme 88 and 89)... 

Chiral 2,2-disubstituted cyclobutanones have been obtained by asymmetric rearrangement of chiral sulfinyl- 177,178 and sulfanylcyclopropanes.179 Using readily available cyclopropyl 4-tolyl (/ )-sulfoxide (l),180 the requisite sulfinylcyclopropanes 3 and 3 were obtained by a sequence of lithiation, reaction with carboxylic acid esters and stereoselective addition of Grignard reagents to the ketones 2 thus formed.178 The corresponding sulfanylcyclopropanes 4 and 4 resulted from a sequence of protection, reduction and deprotection.179... 

Alternatively, the reaction of cyclopropylethynylmagnesium bromide with cyclo-propanone hemiacetal gives l-(cyclopropylethynyl)cyclopropanol (equation 152)232. The reaction of cyclopropanone acetal with other alkynyl Grignard reagents serves as a general route to alkynylcyclopropanols. Similarly, alkynyllithium derivatives of vitamin D were coupled with cyclopropane carbonyl isoxazolidine to give the corresponding alkynyl-cyclopropyl ketones (equation 153). 

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