A phosphine-catalyzed ring-opening addition reaction of cyclopropenones with a variety of nucleophiles (NuH), including oxygen-, nitrogen-, sulfur-, and carbon-based ones, has been investigated, which produces potentially useful α,βunsaturated carbonyl derivatives in high yields (up to 99%), high regioselectivity, and exclusive E-selectivity. The reaction proceeds in high efficiency under very mild conditions using only 1 mol % PPh 3 as the catalyst at room temperature. The method is also amenable for the synthesis of deuterated alkenes when deuterated nucleophiles (NuD) are employed. The mechanism is investigated by experiments and DFT calculations, which suggests an α-ketenyl phosphorus ylide as a key intermediate in the catalytic cycle that captures the nucleophiles in a stereoselective manner.
A highly efficient iodine anion catalyzed cross-dehydrogenative
aromatization of cyclohexenones with amines has been developed under
metal-free conditions, which affords aromatic amines in good to excellent
yields with a broad substrate scope. Meanwhile, this reaction provides
a new method for the construction of C(sp2)–N bonds
and also a new strategy for slow generation of oxidants or electrophiles
via in situ dehalogenation. Moreover, this protocol affords a rapid
and concise approach to chiral NOBIN derivatives.
Bryostatins, a class of naturally occurring macrocyclic lactones with eleven chiral centers, which were isolated from marine invertebrates, turned out as promising candidates for medicinal applications, including AIDS, Alzheimer's disease, and cancer. The ongoing work towards the total synthesis of bryostatins and structural analogues (bryologs) as well as the biomedical application of these compounds is summarized in the Review by J. Jiao, H. Zhang et al. on page 1166 ff.
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