Synthesis and Properties of [2,3‐Bis(trimethylsilyl)‐2‐cyclopropen‐1‐yl]‐diazomethane

Abstract

4j Radical cations of tetrasubstituted alkenes absorb at I,,,, i i 280 nm: P. S. Williams, B. C. Gilbert, R. 0. C. Norman: 3rd Int. Symp. Org. Free Radicals, Poster No. M 21, Freiburg 1981. IS] In unpolar solvents (room temperature) aromatic radical anions release an electron with high quantum yields even upon long wavelength irradiation: U. Sowada, R. A. Holroyd, J. Phys. Chem. 85 (1981) 541. Substituted cyclopropenyldiazomethanespotential precursors of tetrahedraneshave been studied many times. So far, it is not known how a cyclopropenylcarbene behaves in argon at 10 K. In order to reduce the synthetic difficulties we have chosen the trimethylsilyl analogues, in the hope that the protecting groups could be removed at the end of the synthetic sequence[41.The CuBr-catalyzed thermolysis of methyl diazoacetate in presence of bis(trimethylsilyl)acetylene 1 affords the cyclopropenecarboxylic acid ester 2at6! Reduction with diisobutylaluminium hydride leads to alcohol 2b and subsequent oxidation with silver carbonate/celite to aldehyde 2c. Condensation with tosylhydrazide smoothly yields tosylhydrazone 2d (Table I), which reacts with butyllithium to furnish salt 2e. SiMe, H I Me3Si/ SiMes 2a, R = C0,Me; Zb, R = CH,OH; Zc, R = CHO; 2d, R = CH=N-NHTos; Ze, R = CH=N-NLiTos; Zf, R = CHN, Table I. (Selection) 2a-2d : Yields, physical and spectroscopic properties; 'H-NMR (CDCI.,; &values rel. to TMS). All substances gave correct elemental analyses.

Regioselective Formation of β‐Alkyl‐α‐phenyliridabenzenes via Unsymmetrical 3‐Vinylcyclopropenes: Probing Steric and Electronic Influences by Varying the Alkyl Ring Substituent

“…Reduction of esters 9 with excess DIBAL-H [15] afforded alcohols 11 in 75-95 % yield. Unfortunately, use of equimolar amounts of DIBAL-H gave mixtures of the desired aldehyde 12 product along with alcohol 11 and unreacted starting material.…”

Cyclopropenation and Related Reactions of Ruthenium Vinylidene Complexes

“…This molecule has hence been under intense investigation and has played a crucial role in the development of important concepts such as aromaticity and chemical reactivities . Three general methods are known for the synthesis of cyclopropenes: viz., addition of carbene to alkyne, ring closure of vinylcarbene, and 1,2-elimination of a suitable precursor such as halocyclopropane . Two recent papers 2a,b have suggested vinylidene (alkylidenecarbene) to be the intermediate in the thermal rearrangement of cyclopropene: i.e.…”

Chiral Rhodium(II) Carboxamides

“…However, recent advances in the synthesis of cyclopropenes, particularly from rhodium(II) carboxylate catalyzed decomposition of diazo esters in the presence of alkynes (39)(40)(41)(42), has made available an array of stable 3-cyclopropenecarboxylate esters. Previously, copper catalysts provided low to moderate yields of cyclopropenes in reactions of diazo esters with disubstituted acetylenes (43,44), but the higher temperatures required for these carbenoid reactions often led to thermal or catalytic ring opening and products derived from vinylcarbene intermediates (45)(46)(47)(48). Potential uses of the cyclopropene ring as a template in enantiocontrolled synthesis have been recognized, but until now synthetic chiral cyclopropene derivatives have been accessible only through resolution (49).…”