Aminolysis of 3-alkoxysubstituted cyclobutenylidene complexes. A novel convenient route to chiral 3-aminosubstituted cyclobutenylidene complexes

Abstract

Aminolysis of 3-alkoxycyclobutenylidene complexes offers a convienient and high-yield route to a variety of 3-aminocyclobutenylidene complexes. Thus, the 3-diethylaminocyclobutenylidene complexes [(CO) 5 Cr C(C(Me) C(NEt 2) Ç ¹¹¹¹¹¹¹¹¹¹¹º R 2)] [(4), R 2 (CH 2) 5 (a), Me 2 (b), Ph 2 (c)] are obtained by substitution of NEt 2 of diethylamine for the ethoxy group in [(CO) 5 Cr C(C(Me)C(OEt) Ç ¹¹¹¹¹¹¹¹¹º R 2)] (3a-c). The reactions of (R) N-methyl-1-phenylethyl amine and of (S)-2-methoxymethylpyrrolidine with 3a-c afford the 3-N-methyl-(1-phenylethyl)amino-and 3-(2-methoxymethyl-pyrrolidino)-substituted cyclobutenylidene complexes, respectively, as mixtures of the E and Z isomers (with respect to the C3 N bond). Mixtures of the E and Z isomers of 3-(amino acid ester)-substituted cyclobutenylidene complexes are obtained from 3a,b and the methylester of L-leucine, L-phenylalanine, and L-methionine in yields ranging from 82 to 94%. The E/Z ratio strongly depends on the amino acid and the substituents at the sp 3-C atom of the cyclobutenylidene ring. The reactions of 3a-c with cysteine, H 2 N C 2 H 4 SH, proceed highly selectively. Only 3-aminocyclobutenylidene complexes are isolated in 73-86% yield. The formation of 3-organylthiocyclobutenylidene complexes has not been detected. The structure of the E-leucinyl methylester-substituted complex has been established by an X-ray structural analysis.

Addition of Ynamines to the Tungsten η1-Vinylidene Complexes (η5-C5H5)(NO)(CO)WCC(H)R

“…An ORTEP plot of 4a is shown in Figure , crystallographic information are summarized in Table , and selected bond lengths and angles are presented in Table . The W−C(1) distance (2.045(4) Å) in 4a is in the typical range of corresponding 3-aminocyclobutenylidene complexes. 2b,g According to the crystallographic data the cyclobutenylidene ring is not planar but slightly puckered. The angle between the planes formed by the atoms C(1), C(2), C(4) and C(2), C(3), C(4) is 176°.…”

“…The 1 H and 13 C NMR spectra of compounds 4a , b and 5a , b consist of sharp and well-resolved resonance signals. The most informative features in the 13 C NMR spectra are the signals for the carbene carbon atoms located at low field between δ 268 and 271 ppm. 2b,f,g Due to the partial double-bond character, the rotation around the C(3)−N(C 2 H 5 ) 2 bond is hindered and the 1 H NMR spectra of 4a , b and 5a , b show two sets of signals for the ethyl protons. The C(2), C(3), and C(4) signals of 4a , b and 5a , b appear at δ 141−143, 161−166, and 55−61 ppm, respectively, in accordance with the related compounds described in the literature 2f.…”

“…The most informative features in the 13 C NMR spectra are the signals for the carbene carbon atoms located at low field between δ 268 and 271 ppm. 2b,f,g Due to the partial double-bond character, the rotation around the C(3)−N(C 2 H 5 ) 2 bond is hindered and the 1 H NMR spectra of 4a , b and 5a , b show two sets of signals for the ethyl protons. The C(2), C(3), and C(4) signals of 4a , b and 5a , b appear at δ 141−143, 161−166, and 55−61 ppm, respectively, in accordance with the related compounds described in the literature 2f. In the 13 C NMR spectrum of 4b , C(1) and the carbonyl carbon atom at δ 268.7 and 229.4 ppm show satellite signals caused by the coupling with the 183 W atom (14% 183 W abundance; I = 1 / 2 ) with 1 J ( 183 W− 13 C) = 76.3 and 102.7 Hz, respectively.…”

“…The growing research activity in the synthesis of molecule-based materials with second-order nonlinear optical (NLO) properties has produced a wide range of new chromophores . Among them are cyclobutenylidene complexes which are prepared by the reaction of pentacarbonyl vinylidene complexes ((CO) 5 MCCR 2 ; M = Cr, W) with ynamines as well as 1-ethoxypropyne 2b,d Intending to prepare cyclobutenylidene complexes containing a chiral metal atom, we investigated the reaction of tungsten η 1 -vinylidene derivatives Cp(CO)(NO)WCC(H)R with ynamines.…”

“…Among them are cyclobutenylidene complexes which are prepared by the reaction of pentacarbonyl vinylidene complexes ((CO) 5 MCCR 2 ; M = Cr, W) with ynamines as well as 1-ethoxypropyne 2b,d Intending to prepare cyclobutenylidene complexes containing a chiral metal atom, we investigated the reaction of tungsten η 1 -vinylidene derivatives Cp(CO)(NO)WCC(H)R with ynamines. Surprisingly, the substituent R on the C β atom of the vinylidene complex dramatically influenced the outcome of the reaction and gave rise to a wide range of different products.…”