Efficient Conjugate Reduction of α,β-Unsaturated Carbonyl Compounds by Complexation with Aluminum Tris(2,6-diphenylphenoxide)

Designer Lewis acid catalysts—bulky aluminium reagents for selective organic synthesis

“…Efficient conjugate reduction of several a,b-unsaturated carbonyl substrates was similarly realized by the combined use of ATPH and diisobutylaluminium hydride-butyllithium 'ate' complex (DIBAL-H-Bu n Li) as a reducing agent (Scheme 15). 25 Diisobutylaluminium hydride-tert-butyllithium (DIBAL-H-Bu t Li) was more effective for the 1,4-reduction of a,bunsaturated aldehydes.…”

Stereodivergent conjugate reduction of α-substituted α,β-unsaturated N-sulfinyl ketimines: flexible access to challenging acyclic β,β-disubstituted enesulfinamides

“…Reduction of 1a′ with NaBH 4 /NiCl 2 and NaBH 4 /CoCl 2 generated a conjugate reduction product with moderate to low stereoselectivities (entries 6 and 7), while NaBH 4 /CuCl 2 was inert, and 1a′ remained intact (entry 8). 15 The combination of aluminum tris(2,6-diphenylphenoxide) (ATPH) and tetradentate aluminum hydride, developed by Yamamoto for 1,4-reduction of enones and enals, 16 facilitated the reduction of unsaturated ketimine 1a′ , giving ( E )- 2a in 73% yield with high stereoselectivity (entry 9). In this case, the competing 1,2-reduction also occurred (13% yield), suggesting that ATPH could not completely block the N-t BS imino group in ketimine 1a′ as effectively as it did during the reduction of unsaturated carbonyls.…”

A Programmable Synthesis of Diverse Terpene Architectures from Phenols

“…We began by exploring the scope of the initial dearomatization using bulky aluminum Lewis acids such as MABR and MAD (22 and 23, respectively, Figure 2) as developed by Yamamoto. 6,23,24 This reaction has been rarely employed despite its potential; to the best of our knowledge there has been only one use (with one substrate), in natural product synthesis, racemically by Danishefsky 25 and asymmetrically by Lawrence. 26 As such, we have more fully explored the scope of the dearomatization with 22 and 23, and as denoted below, have developed a related reaction, a one-pot reductive dearomatization, in which one of the enones is reduced to afford compounds like 6 and 8.…”