It's as easy as 1, 2, 3: In a one-pot sequence, two stereocenters and three new bonds were created with high selectivity through an asymmetric alkynylation of acyl silanes, a tandem Brook-type rearrangement and Zn-ene-allene cyclization, the addition of an electrophile, and finally oxidation. The straightforward nature of the synthetic procedure contrasts strongly with the complexity of the densely functionalized products obtained.

Diastereoisomerically pure (dr > 99:1) and enantiomerically enriched (er up to 98:2) substituted propargyl diols possessing a tertiary hydroxyl group were synthesized in a single-pot operation from simple acylsilanes through a combined catalytic enantioselective alkynylation of acylsilanes, followed by an allenyl-Zn-Brook rearrangement and Zn-ene-allene (or Zn-yne-allene) cyclization reaction. Two remarkable features of these reactions are the near complete transfer of chirality in the allenyl-Zn-Brook rearrangement and the highly organized six-membered transition state of the Zn-ene-allene carbocyclization found by DFT calculations. In this process, three new bonds and two new stereogenic centers are created in a single-pot operation in excellent diastereo- and enantiomeric ratios. DFT calculations show that the allenyl-Zn-Brook rearrangement occurs in preference to the classic [1,2]-Zn-Brook rearrangement owing to its significantly lower activation barrier.

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Systems. -(SMIRNOV, P.; MATHEW, J.; NIJS, A.; KATAN, E.; KARNI, M.; BOLM, C.; APELOIG, Y.; MAREK*, I.; Angew. Chem., Int. Ed. 52 (2013) 51, 13717-13721, http://dx.