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Table 2 Scope of reaction for the addition of 2 to 1 in the presence of 3da
products series was assigned by the correlation with a known
compound in the literature (6a) and by circular dichroism. It was
determined as R, assuming the same stereochemical outcome for
all the compounds 4, 5 and 6 (see the ESI†).
In conclusion, we have described an asymmetric Mukaiyama–
Michael reaction of silyl dienolates to a,b-unsaturated acyl
phosphonates as ester surrogates. The employed bifunctional
organocatalyst orchestrated the approach of the silyloxy diene to
the Michael acceptor, leading to the formation of Rauhut–
Currier type esters. The reaction proceeded under mild conditions
with complete regioselectivity, excellent enantiocontrol and a
reasonably high range of a,b-unsaturated phosphonates. In addi-
tion, the methodology led to tri- and tetra-substituted Rauhut–
Currier type esters.
We are grateful to the Spanish Government (CTQ2015-64561-R
and CTQ2016-76061-P) and the European Research Council (ERC-
CG-UNBICAT, contract number: 647550). J. A. F.-S. and V. L.-M.
thank the Spanish Government for a Juan de la Cierva Contract
´
and the Universidad Autonoma de Madrid for a predoctoral
fellowship (FPI-UAM), respectively. Financial support from the
Spanish Ministry of Economy and Competitiveness, through the
‘‘Maria de Maeztu’’ Program of Excellence in R&D (MDM-2014-
0377), is also acknowledged. We acknowledge the generous
allocation of computing time at the CCC (UAM).
a
Conflicts of interest
All the reactions were performed on a 0.1 mmol scale in 0.6 mL of
p-xylene. Enantiomeric excess was determined by SFC chromatography.
There are no conflicts to declare.
Notes and references
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2 For selected general reviews on the R–C reaction, see:
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S. E. Schaus, in Lewis Base Catalysis in Organic Synthesis, ed. E. Vedejs
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Scheme 2 (a) Control experiment and isolation of intermediate 4a. Proposed
coordination model. (b) Derivatization of dihydropyranone derivatives 4 to
compounds 6a and 6b.
5,6-dihydropyran-2-one moiety is of considerable interest from a
chemical and pharmacological perspectives.14 Taking advantage of
the enantioselective formation of lactone 4a, 4,5-disubstituted
dihydropyranones 6a and 6b were obtained with excellent enantio-
selectivities via simple alkene metathesis with styrene (Scheme 2,
eqn (b)). The absolute configuration of the Rauhut–Currier type
4 For selected reviews, see: (a) S. B. J. Kan, Kenneth K.-H. Ng and
I. Paterson, Angew. Chem., Int. Ed., 2013, 52, 9097–9108; (b) J.-i.
Matsuo and M. Murakami, Angew. Chem., Int. Ed., 2013, 52,
9109–9118; (c) S. Hosokawa, Tetrahedron Lett., 2018, 59, 77–88;
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Chem. Commun., 2018, 54, 13941--13944 | 13943