Herein a direct β-sulfido carbonyl compound synthesis by the easy activation of RS-Bpin reagents with α,β-unsaturated ketones and aldehydes is reported. This convenient methodology can be performed at room temperature with no other additives. The key point of this reactivity is based on the Lewis acidic properties of the boryl unit of the RS-Bpin reagent interacting with the C═O oxygen. Consequently, the SR unit becomes more nucleophilic and promotes the 1,4- versus the 1,2-addition, as a function of the involved substrate. The thioborated products can be further transformed into β-sulfido carbonyl compounds by addition of MeOH.
Abstract:The" pull-push" effect of the Bpin moiety in ArE-Bpin reagents (E = Se,S )i sd emonstrated by the Lewis acid interaction with the carbonyl group of ynones andthe concomitant delivery of ArSe or ArSt ot he electron-deficient alkyne with impressive stereoselectivity.T he two component reactivity is carriedo ut in methanol to generate (Z)-b-(arylseleno)-a,b-unsaturated ketones and (Z)-b-(arylsulfuro)-a,b-unsaturated ketones with ac onsensus between experimental andt heoretical understanding of the mechanism.
The insertion of the diazo derivative Me3SiCHN2 into pinB-SR σ bonds (R = Ph, Tol, Bn) allows a direct synthesis of multisubstituted H-C(SR)(Bpin)(SiMe3) compounds. Consecutive base-assisted transformations of HC(S)(B) (Si) systems lead to deborylative alkylations, Sommelet-Haüser rearrangements, and deprotoalkylations. Intramolecular cyclizations can be selectively performed either via desilylative or deborylative manifolds by fine-tuning the base employed.
Diboron reagents can be activated both, from a metal or free-metal context, and consequently the addition of boryl units to unsaturated substrates proceeds sometimes with complementary selectivity. We highlight here the power of boron chemistry to functionalize molecules and provide new routes towards challenging compounds.
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