An exceptionally general electrophilic amination, which directly transforms commercially available nitroarenes into alkylated aromatic aminoboranes with zinc organyl compounds was developed. The reaction starts with a two-step partial reduction of the nitro group to a nitrenoid, which is used in situ as the electrophilic amination reagent. To facilitate isolation, the resulting air- and moisture-sensitive aminoboranes were reacted with a range of electrophiles. The method not only represents a direct transformation of nitro compounds into electrophilic amination reagents but also provides an elegant alternative to dehydrocoupling methods for the generation of aminoboranes.

Supercritical carbon dioxide is the preferred reaction medium for catalyst synthesis as exemplified for the hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL).

Ar are reductive coupling of nitro compounds with organohalides has been realized. The reaction is initiated by ap artial reduction of the nitro group to an itrenoid intermediate.T herefore,n ot only aromatic but also aliphatic nitro compounds are efficiently transformed into monoalkylated amines,w ith organohalides as the alkylating agent. Given the innate reactivity of the nitrenoid, ac atalyst is not required, resulting in ahigh tolerance for aryl halide substituents in both starting materials. Scheme 1. Reductivec oupling strategies. Table 2: Scope of the reductive coupling of nitro compounds with organohalides.Reaction conditions: Zn powder (4 equiv) and LiCl (2.2 equiv) were dried in vacuo, 1mLTHF was added, followed by pretreatment with catalytic amounts of TMSCl and dibromoethane. R 1 X 2 (0.6 mmol, 3equiv), the nitro compound 1 (0.2 mmol), and B 2 pin 2 (0.4 mmol, 2equiv) were added and the reaction was stirred for 12 hatRT. The aminoborane D was hydrolyzed by addition of water.[a] Carried out at 50 8 8C.[b] Reaction stirred for 1hat 50 8 8Cbefore the addition of 1a.[c] Carried out at 70 8 8C. Structures, compound numbers, and yields of isolatedproducts after column chromatography are given.

The first transition metal-free cycloisomerization of easily accessible diynols is presented as a novel approach to bicyclic 2H-pyrans. As a one-step protocol, the reaction proceeds in a single reaction cascade by intertwining mechanistic fragments borrowed from transition metal-catalyzed Claisen rearrangment of vinyl ethers with our own work on allenyl/propargyl cation rearrangements and a 6π-oxo-electrocylization. It is enabled by a new cooperative catalytic system that combines a simple Ca(2+) catalyst with camphorsulfonic acid.

The first general protocol for the direct reductive N-functionalization of aliphatic nitro compounds is presented. The nitro group is partially reduced to a nitrenoid, with a mild and readily available combination of B pin and zinc organyls. Thereby, the formation of an unstable nitroso intermediate is avoided, which has so far severely limited reductive transformations of aliphatic nitro compounds. The reaction is concluded by an electrophilic amination of zinc organyls.

In analogy to the classical reaction of C-B bonds with peroxides, the first oxidative functionalization of aminoboranes through a 1,2-N migration was realized. Readily available aliphatic nitro compounds are thereby transformed into N- and O-functionalized hydroxylamines in a single synthetic operation. Addition of hazardous peroxides is avoided. Instead, the insertion of O , as the terminal oxidant, into Zn-C bonds provides the necessary peroxides. The required zinc organyls, in turn, are formed through a boron-to-zinc exchange, from an organoboronic ester byproduct of the nitro-to-aminoborane transformation.

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An exceptionally general electrophilic amination, which directly transforms commercially available nitroarenes into alkylated aromatic aminoboranes with zinc organyl compounds was developed. The reaction starts with at wostep partial reduction of the nitro group to anitrenoid, whichis used in situ as the electrophilic amination reagent. To facilitate isolation, the resulting air-a nd moisture-sensitive aminoboranes were reacted with arange of electrophiles.The method not only represents ad irect transformation of nitro compounds into electrophilic amination reagents but also provides an elegant alternative to dehydrocoupling methods for the generation of aminoboranes.