An Alkynylboronic Ester Cycloaddition Route to Functionalized Aromatic Boronic Esters.

Abstract

Organo-boron compounds S 0040An Alkynylboronic Ester Cycloaddition Route to Functionalized Aromatic Boronic Esters. -Functionalized aromatic boronic esters are obtained by regioselective cycloaddition of alkynylboronates (II) with 2-pyrones, e.g. (I), (V) and (VI). A regiochemistry pattern is found that suggests that the most favored mode of reaction is the addition of the boron substituted alkyne carbon to the carbon atom adjacent to the ester oxygen. The selectivity is further modulated by substituents on the alkyne and the pyrone substrates. -(DELANEY, P. M.; MOORE, J. E.; HARRITY*, J. P. A.; Chem. Commun. (Cambridge) 2006, 31, 3323-3325; Dep. Chem., Univ. Sheffield, Sheffield S3 7HF, UK; Eng.) -M. Paetzel 51-169

Recent Advances in the Synthesis of 2-Pyrones

“…The cycloadditions of 3,5-dibromo-2-pyrone ( 143 ) with substituted acetylenes including alkynylboronates and 1,2-bis(trimethylsilyl)acetylene (BTMSA) deliver a series of functionalized aromatic compounds without any further treatment ( Scheme 44 ) [ 67 , 68 ]. It is of note that the selectivity is modulated by substituents on the alkynes.…”

“…It is of note that the selectivity is modulated by substituents on the alkynes. Therefore, an excellent regioselectivity was observed with phenyl- or n -Bu substituted boronates whereas an equal mixture of regioisomers was generated with the trimethylsilyl substituted acetylene ( Scheme 44 ) [ 67 ].…”

Synthesis and Applications of Group 14-metalated Arylboranes

“…64, 67-69 via [4+2] cycloaddition with reactive cyclic dienes such as substituted cyclopentadienone 63 (Scheme 26) and 2-pyrone derivatives 65-66 (Scheme 27)[36][37][38].…”