Cascade Synthesis of Pyrrolo[1,2-]quinolines and Pyrrolo[2,1-]isoquinolines via Formal [3 + 2]-Cycloaddition of Push-Pull Nitro Heterocycles with Carbonyl-Stabilized Quinolinium/Isoquinolinium Ylides.

Various substituted pyrrolo[1,2-]quinolines and pyrrolo[2,1-]isoquinolines were synthesized in good to high yields by the EtN-mediated reaction of push-pull 3-nitrobenzofurans or 1-Ts-/1-Ms-3-nitroindoles and precursors of carbonyl-stabilized quinolinium and isoquinolinium ylides as 1,3-dipole equivalents. These transformations proceed in a one-pot manner starting with the formal [3 + 2]-cycloaddition stage, which is accompanied by double dearomatization of both quinoline/isoquinoline and benzofuran/indole moieties, followed by ring-opening of cyclic intermediate formed and nitrous acid elimination sequence. [3 + 2]-Cycloadducts were isolated as the final products in cases of impossibility or difficulty of their enolization.

Divergent Transformations of 2-Nitro-1-benzo[]chromenes in Reactions with Alkylidenemalononitriles: Access to Naphtho[2,1-]furans via Base-Mediated Pyran Ring Contraction.

The action of 2-(1-arylethylidene)malononitriles on 2-nitro-1-benzo[]chromenes in the presence of EtN and MoO·2HO results in naphtho[2,1-]furans containing an allylidenemalononitrile unit in the α-position. The reaction proceeds with contraction of the pyran ring via a cascade carba-Michael addition/retro-oxa-Michael reaction/tautomerization/S2/oxidation process. In contrast, the reaction of 2-nitro-1-benzo[]chromenes with the cyclic Knoevenagel adduct derived from 1-indanone and malononitrile leads to dihydroindeno[1,2-]xanthenes.

Testing and improving the performance of protein thermostability predictors for the engineering of cellulases.

Thermostability of cellulases can be increased through amino acid substitutions and by protein engineering with predictors of protein thermostability. We have carried out a systematic analysis of the performance of 18 predictors for the engineering of cellulases. The predictors were PoPMuSiC, HoTMuSiC, I-Mutant 2.

Catalyst-free formal [3 + 2] cycloaddition of stabilized ,-cyclic azomethine imines to 3-nitrobenzofurans and 3-nitro-4-chromenes: access to heteroannulated pyrazolo[1,2-]pyrazoles.

We have studied the [3 + 2]-cycloaddition of various ,-cyclic azomethine imines to 3-nitrobenzofurans. This process is a rare example of their dearomatization. We have also extended this process to the related 3-nitro-4-chromenes as dipolarophiles.