gamma-hydroxy unsaturated nitriles: chelation-controlled conjugate additions

A Unified Approach for the Assembly of Atisine- and Hetidine-type Diterpenoid Alkaloids: Total Syntheses of Azitine and the Proposed Structure of Navirine C

A tetracyclic dinitrile was synthesized in twelve steps from cyclohex-2-en-1-one by using a chelation-triggered conjugate addition to a γ-hydroxy-substituted α,β-unsaturated nitrile and an oxidative dearomatization/Diels-Alder cycloaddition cascade as the key steps. The first total synthesis of azitine (in 17 steps) was achieved through a simple reductive cyclization of this intermediate and subsequent transformations while the total synthesis of the proposed structure of navirine C (in 19 steps) was accomplished by a hydrogen-atom-transfer reaction of the tetracyclic dinitrile, Pd/C-catalyzed reductive cyclization, and subsequent functional group manipulation.

G3 assisted rational design of chemical sensor array using carbonitrile neutral receptors

Combined computational and experimental strategies for the systematic design of chemical sensor arrays using carbonitrile neutral receptors are presented. Binding energies of acetonitrile, n-pentylcarbonitrile and malononitrile with Ca(II), Mg(II), Be(II) and H⁺ have been investigated with the B3LYP, G3, CBS-QB3, G4 and MQZVP methods, showing a general trend H⁺ > Be(II) > Mg(II) > Ca(II). Hydrogen bonding, donor-acceptor and cation-lone pair electron simple models were employed in evaluating the performance of computational methods. Mg(II) is bound to acetonitrile in water by 12.5 kcal/mol, and in the gas phase the receptor is more strongly bound by 33.3 kcal/mol to Mg(II) compared to Ca(II). Interaction of bound cations with carbonitrile reduces the energies of the MOs involved in the proposed σ-p conjugated network. The planar malononitrile-Be(II) complex possibly involves a π-network with a cationic methylene carbon. Fabricated potentiometric chemical sensors show distinct signal patterns that can be exploited in sensor array applications.

Gamma-hydroxy-alpha,beta-alkenenitriles: chelation-controlled conjugate additions

Temporarily anchoring Grignard and organolithium reagents to gamma-hydroxy-alpha,beta-alkenenitriles promotes efficient conjugate additions to what are otherwise recalcitrant Michael acceptors. Sequential deprotonation and addition of a modest excess of a second Grignard reagent allows effective conjugate delivery of alkyl groups to cyclic and acyclic alkenenitriles. Mechanistically, conjugate additions proceed through alkylmagnesium alkoxide complexes for all but the more substituted alkenenitriles that require alkyl transfers from the more reactive ate complexes. Synthetically, chelation-controlled conjugate additions rapidly, and stereoselectively, assemble substituted nitriles, installing up to two new stereocenters in a single synthetic operation.

Alkenenitriles: annulations with omega-chloro Grignard reagents

[reaction: see text] omega-Chloro Grignard reagents chelate with cyclic gamma-hydroxy-alpha,beta-alkenenitriles to trigger a conjugate addition-alkylation annulation. The chelation-controlled conjugate addition-alkylation is the first anionic annulation with alpha, beta-alkenenitriles, providing cis bicyclo[3.3.0]octane, hydrindane, and decalin ring systems in a single synthetic operation.

Alkynenitriles: chelation-controlled conjugate additions

[reaction: see text] Chelation between gamma-hydroxybutynenitrile and Grignard reagents triggers a particularly facile anionic conjugate addition reaction. Structurally diverse Grignard reagents add with equal efficiency, providing an intermediate anion that stereoselectively alkylates benzaldehyde in an overall addition-alkylation reaction.

Hydrocarbon activation. Synthesis of beta-cycloalkyl (di)nitriles through photosensitized conjugate radical addition

Photoinduced hydrogen abstraction from aliphatic cyclic hydrocarbons (C(5) to C(7), C(12), as well as adamantane) by triplet aromatic ketones in the presence of alpha,beta-unsaturated (di)nitriles offers a straightforward entry to the corresponding alkylated (di)nitriles via the alkyl radicals. Yields are moderate to good depending on the olefins structure (substitution in beta slows down the addition to mononitriles, but with alpha,alpha-dinitriles electronic activation allows efficient alkylation also of beta,beta-disubstituted substrates). A tandem alkylation-cyclization process has been obtained with (1-methylpent-4-enylidene)malononitrile.