By -sigmatropic rearrangement

Formation of five-member N,S- and N-heterocycles by sigmatropic rearrangements of functionalized allenes 97FA2005. 

The field of allenes bearing phosphorus is dominated by sigmatropic rearrangements (see Section 1.3.1). Nevertheless, some examples of prototropic rearrangements are known. 

The glycosid-3-ulose derivative 208 was obtained from the corresponding D-ido alcohol by use of acetic anhydride-dimethyl sulfoxide for 4 h at room temperature. However, when the time was extended to 4 days, the doubly branched product 209 was obtained, by sigmatropic rearrangement of the intermediate 210.423... 

The structure of 6-exo-ethoxycarbonyl-2,3a,4,6a-tetraphenyl-3,3a,4,5,6,6a-hexahydropyrrolo [2,3-cf]-1,2,3-triazol-2-ium-3-ide (6) has been determined compound (6) arises from an initial 1,3-dipolar cycloaddition between ethyl acrylate and the dipole (7), followed by sigmatropic rearrangements <90JCS(P1)2537>. 

Butler and co-workers prepared an example of the furo[2,3-d]-l,2,3-triazole ring system by reaction of the 1,2,3-triazolium 1-oxide (116) with JV-phenylmaleimide, yielding 75% of the stable triazol-2-ium-3-ide (117) which is the result of a 1,3-dipolar cycloaddition followed by sigmatropic rearrangements <90JCS(Pl)332l>. 

Naturally occurring compounds that possess as part of their structures bicyclo[5.3.0]decane and bicy-clo[5.4.0]undecane skeletons are very common in the terpenoid family of natural products. Since both of these carbon frameworks are readily prepared by sigmatropic rearrangement of 3-(2-vinylcyclopropyl) enones, it is not surprising that this method has been applied to the total synthesis of terpenoids. 

Ritter, K. Formation of C-N bonds by sigmatropic rearrangements, in Houben-Weyl. Stereoselective Synthesis (eds. Hoffmann, R. W., Mulzer, J.,Schaumann, E.), 9, 5677-5699 (Thieme, Stuttgart, 1995). 

Formation of C-C Bonds by Sigmatropic Rearrangements and Electrocyclic Reactions... 

The formation of C-O and C-N bonds by sigmatropic rearrangements is referred to in this section only for the sake of completeness. For more detailed discussion on these subjects see Section D.4.11. (C-O bond formation) and Section D.7.6. (C N bond formation). 

Mulzer J, Bats JW, List B, Opatz T, Trauner D (1997) The phenanthrenone approach to opium alkaloids formal total synthesis of morphine by sigmatropic rearrangement. Synlett 441 44... 

Another class of reactions that can occur by sigmatropic rearrangements involve alkyl group shifts ... 

Vedejs has reported an oxaza-Claisen rearrangement to construct the pyrrole derivative 38. In presence of ethyl propiolate, the vinylogous hydroximic acid 35 imdergoes a conjugate addition followed by sigmatropic rearrangement to produce the aldehyde 37. Cyclization and dehydration resulted 38. ... 

Reduction of a carbon-carbon triple bond of acetylene produces the optically active cis or trans allylic alcohols. The functionality and chirality of the alcohol center may then be transferred by sigmatropic rearrangement [17] or by dis-... 

Knoevenagel reactions followed by sigmatropic rearrangements or electrocyclizations ... 

Barbazanges M, Meyer C, Cossy J, Turner P. Synthesis of 1,2-amino alcohols by sigmatropic rearrangements of 3-(JV-tosylamino)aUylic alcohol derivatives. Chem. Eur. J. 2011 17(16) 448(L4495. 

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