[4+2]Cycloadditions of organometallic-substituted siloles with dimethyl acetylenedicarboxylate and tetracyanoethylene

Boron-Substituted Building Blocks in Diels-Alder and Other Cycloaddition Reactions

“…Accordingly, the group of Lallemand applied this strategy towards the synthesis of clerodin (35). 13,14,15 Cycloadduct 33, which was generated in the Diels-Alder reaction of 32 with methyl acrylate and aldehyde 29 (Scheme 11), was further converted successfully into the bicyclic product 34.…”

“…Instead of using boronic esters in the 2-position of the diene, Wrackmeyer introduced dialkylboranes as the boron functionality. 35 The diethylborane-functionalised siloles 73 participated in [4+2] cycloadditions at room temperature in benzene within minutes in quantitative yields (Scheme 26).…”

Combination of 1,2‐hydroboration and 1,1‐organoboration: synthesis of novel organo‐substituted 1‐silacyclobutenes

“…The reagent 'Et 2 BH' 17 was prepared as described and the hydride concentration (1.17%) was determined by 11 B NMR spectroscopy. 47 Mass spectra (EI, 70 eV): Finnigan MAT 8500 with direct inlet; the m/z data refer to the isotopes 1 H, 11 B, 12 C, 28 Si. NMR measurements in C 6 D 6 (concentration ca 5-10%) .…”

“…Recently, it has been shown that 1,2-hydroboration using 9-BBN can be regiospecific even in the presence of two different silyl groups at the C C bond. 12 This has led to useful synthons for heterocyclic chemistry, such as A or B. Treatment of A or B with lithium alkynides should give either borates C or new alkyn-1-ylsilanes such as D, both of which could undergo intramolecular rearrangements corresponding either to the reactions of alkyn-1-ylborates with electrophiles 13 -15 or to 1,1-organoboration reactions.…”

Synthesis and Applications of Group 14-metalated Arylboranes

“…cyclopentadiene 77 bearing a diethylboryl group in the 3-position and a trimethylstannyl group in the 5-position undergoes [4+2]cycloaddition with dimethyl acetylenedicarboxylate 78 to give a 7-silanorbornadiene 79 rearranging into a benzene derivative 80 by the formation of a Si O bond and the 1,3-migration of the trimethylstannyl group (Scheme 31)[42].…”