Research On Environmentally Friendly Synthesis Technology Of Nitrogen-containing Organoboron Compounds

Organoboron compounds,especially boronic acids,[R–B(OH)2] and pinacol-or neopentyl glycol-derivedesters [R–B(pin)or R–B(neop)],have been regarded as indispensable organometallic reagents in modern synthetic organic chemistry for constructing carbon–carbon and carbon–heteroatom bonds,owing to their easiness to handle,high availability,low toxicity,high functional group-compatibility,etc.Their reactivities are mainly governed by Lewis acidity of the boron center,where a Lewis base coordinates to the 2p empty orbital to generate a borate as an active species,being a key intermediate in various transformations.Moreover,doping of polycyclic aromatic hydrocarbons(PAHs)with boron-nitrogen units,i.e.,isoelectronic and isosteric replacement of a C=C bond with a B-N bond,has emerged as a versatile strategy for the preparation of novel hybrid PAHs with unusual andattractive optical,electronic and chemical properties that are absent from their C=C congener.In 2007,Suginome and Burke independently reported on boron-masking strategy in Suzuki–Miyaura coupling(SMC)using naphthalene-1,8-diaminato(dan)and N-methyliminodiacetoxy(mida)as a boron Lewis-acidity-diminishing substituent;the respective B(dan)and B(mida)moieties become inert toward transmetalation,and thus enabling iterative SMC to occur chemoselectively to lead to the convenient and efficient synthesis of complex oligoarenes and natural products(Scheme 1).In addition,Suginome also developed another Lewis acidity diminished boron moiety,B(aam)(aam: anthranilamidato),being usable for the iterative SMC.However,However,traditional methods for synthesizing B(dan)and B(aam)have some limitations,such as the need to use expensive metal catalysts,high temperature,or complicated operation steps.This paper investigates the efficient,simple,and green synthesis of "masked" arylboronic acids R-B(dan)and 1,3,2-benzodiazaboranones [R-B(aam)] in two parts.Part 1: Synthesis of R(alkyl or aryl)-B(dan)An environment-friendly methodology for the synthesis of R(alkyl or aryl)-B(dan)on water is described.1,8-diamino naphthalene(dan H2)was reacted with different types of organoboronic acids to furnish the products in moderate to excellent yields.A multi-gram scale reaction is also performed to ensure the scalability of the reaction.Part 2: Synthesis of 1,3,2-benzodiazaborininones [R-B(aam)]A simple,efficient and mild methodology for the synthesis of 1,3,2-benzodiazaborininones [R-B(aam)] from boronic acids and anthranilamides on ethyl acetate is described.A series of 1,3,2-benzodiazaborininones were prepared in moderate to excellent yields at room temperature without dehydrating agents,metal catalysts,corrosive acids or other additives.Meanwhile,a multi-gram scale reaction is also performed to ensure the scalability of the reaction,and the product can be conveniently isolated by simple filtration.