Dimethylamine adducts of allylic triorganoboranes as effective reagents for Petasis-type homoallylation of primary amines with formaldehyde.

Dimethylamine adducts of triallyl-, triprenyl- and trans-cinnamyl(dipropyl)borane are effective reagents for mild homoallylation of primary amines with aqueous formaldehyde in MeOH without an inert atmosphere. A new concept is proposed for the explanation of the high stability of allylborane-amine adducts in aqueous MeOH.

Adducts of Triallylborane with Ammonia and Aliphatic Amines as Stoichiometric Allylating Agents for Aminoallylation Reaction of Carbonyl Compounds.

Triallylborane-amines adducts are effective stoichiometric allylating agents in the aminoallylation reaction of carbonyl compounds in methanol. Moreover, copper-catalyzed diastereoselective allylation of Ellman's imine was achieved with triallylborane-methylamine adduct.

Stereoselective synthesis of novel adamantane derivatives with high potency against rimantadine-resistant influenza A virus strains.

A series of (R)- and (S)-isomers of new adamantane-substituted heterocycles (1,3-oxazinan-2-one, piperidine-2,4-dione, piperidine-2-one and piperidine) with potent activity against rimantadine-resistant strains of influenza A virus were synthesized through the transformation of adamantyl-substituted N-Boc-homoallylamines 8 into piperidine-2,4-diones 11 through the cyclic bromourethanes 9 and key intermediate enol esters 10. Biological assays of the prepared compounds were performed on the rimantadine-resistant S31N mutated strains of influenza A - A/California/7/2009(H1N1)pdm09 and modern pandemic strain A/IIV-Orenburg/29-L/2016(H1N1)pdm09. The most potent compounds were both enantiomers of the enol ester 10 displaying IC50 = 7.7 µM with the 2016 Orenburg strain.

Structure and bonding nature of the strained Lewis acid 3-methyl-1-boraadamantane: a case study employing a new data-analysis procedure in gas electron diffraction.

Base-free 3-methyl-1-boraadamantane was synthesized by starting from its known THF adduct, transforming it to a butylate-complex with n-butyllithium, cleaving the cage with acetyl chloride to give 3-n-butyl-5-methyl-7-methylene-3-borabicyclo[3.3.1]nonane and closing the cage again by reacting the latter with dicyclohexylborane. The identity of 3-methyl-1-boraadamantane was proven by (1) H, (11) B and (13) C NMR spectroscopy and elemental analysis. The experimental equilibrium structure of the free 3-methyl-1-boraadamantane molecules has been determined at 100 °C by using gas-phase electron diffraction. For this structure determination, an improved method for data analysis has been introduced and tested: the structural refinement versus gas-phase electron diffraction data (in terms of Cartesian coordinates) with a set of quantum-chemically derived regularization constraints for the complete structure under optimization of a regularization constant, which maximizes the contribution of experimental data while retaining a stable refinement. The detailed analysis of parameter errors shows that the new approach allows obtaining more reliable results. The most important structural parameters are: r(e) (B-C)(av) =1.556(5) Å, angle(e) (C-B-C)(av) =116.5(2)°. The configuration of the boron atom is pyramidal with ∑ angle (C-B-C)=349.4(4)°. The nature of bonding was analyzed further by applying the natural bond orbital (NBO) and atoms in molecules (AIM) approaches. The experimentally observed shortening of the B-C bonds and elongation of the adjacent C-C bonds can be explained by the σ(C-C)→p(B) hyperconjugation model. Both NBO and AIM analyses predict that the B-C bonds are significantly bent in the direction out of the cage.

Design of bicyclic and cage boron compounds based on allylboration of acetylenes with allyldichloroboranes.

Allylboration of acetylenes with allyldichloroboranes has been proposed as a first step of allylboron-acetylene condensation and a way to design condensation products from stage to stage. The chemistry has been applied to the synthesis of isomeric 3-borabicyclo[3.3.1]non-6-enes transformed into 3-methyl-1-boraadamantane and [5-D]-3-methyl-1-boraadamantane derivatives.

Reactivity of 1,6-bis(trimethylsilyl)-hexa-3-ene-1,5-diynes towards triethylborane, triallylborane, and 1-boraadamantane: first molecular structure of a 4-methylene-3-borahomoadamantane derivative, and the first 6,8-diborabicyclo[2.2.2]oct-2-ene derivative.

Compounds (E)- (1) and (Z)-1,6-bis(trimethylsilyl)-hexa-3-ene-1,5-diyne (2) react with triethylborane (3) by 1,1-ethylboration in a 1:1 or 1:2 molar ratio (in the case of 1), whereas in the case of 2 only the 1:1 product is formed. The analogous reactions of 1 or 2 with triallylborane (4) are more complex because of competition between 1,1-allyl- and 1,2-allylboration. Again, compound 2 reacts only with one equivalent of 4. In the case of 1-boraadamantane (5), 1,1-organoboration of 1 and 2 takes place either at one or at both C[triple bond]C bonds leading to compounds containing the 4-methylene-3-borahomoadamantane unit(s). The product of the reaction of 1 with two equivalents of 5 was characterized by X-ray structure analysis. The primary products of the reaction of 2 with 5 rearrange upon heating by deorganoboration and organoboration to give finally a tetracyclic compound 24 that contains an exocyclic allenylidene group. The product of the 1:2 reaction of 2 with 5 rearranges to give the 6,8-dibora-bicyclo[2.2.2]oct-2-ene derivative 25. All reactions were monitored by (1)H, (11)B, (13)C, and (29)Si NMR spectroscopy.