Metal-assisted cycloadditions. Part 1. Synthesis of substituted cyclopentane-derivatives obtained from the reactions of (η¹-allyl)dicarbonyl(η⁵-cyclopentadienyl)iron with electron-deficient olefins and acetylenes

Abstract

Bei Einwirkung der Olefine (II) auf den o‐Allyl‐Fe‐Komplex (I) entstehen die Cyclopentylderivate (III), während die Reaktion von (I) mit dem Acetylen (IV) mit 54% Gesamtausb.

Metal-Assisted Cycloaddition Reactions in Organotransition Metal Chemistry

“…296,301,308 The most widely used L n M fragment is (η 5 -cyclopentadienyl)-dicarbonyliron (Fp). As the removal of an Fp group is often readily accomplished by a variety of methods (replacement by H, 310,311 COCl or COOMe, [311][312][313][314][315][316] halogen, 309,311,313 or NH 2 317 ), these cycloadditions present a great potential also for organic synthesis as exemplified by the synthesis of, e.g., hydrazulenes, 318 trisubstituted cyclopentene, 310,311 (()-sarkomycin. 319 [Reference 309 gives a list of references on mechanistic, kinetic, and stereochemical investigations on the cleavage of compounds of the general formula cpFe(CO)LR by electrophiles EX to yield RE and cpFe(CO)LX.]…”

Fe Organoiron Compounds Part B13

“…The reaction of FpCH 2 CH=CH 2 with two equivaLents of CH 3 00CC=CCOOCH 3 in dimethyLformamide at room temperature for 90 h affords the cycLic compound LlV (R1 = H) (42% yieLd), FpC(COOCH 3 )=C(COOCH 3 )CH 2 CH=CH 2 (9%), and FpCH 2 CH=CHC(COOCH 3 )= CHCOOCH 3 (3%) [172], see aLso [142,143]. It is assumed that the coLLapse of the intermediate dipoLar zwitterion LV follows three routes: (a) cycLization, (b) insertion, and (c) H-transfer [172].…”

“…(Z)-FpCH 2 CH= CHOCH 3 gives onLy the cycLic product LlV (R1 =OCH 3 , 77%), when it is combined with four equivaLents of CH 3 00CC=CCOOCH 3 in dimethylformamide at room temperature for 48 h, followed by addition of another two equivaLents and stirring further for 24 h. It is suggested that the absence of Linear products might be due to the presence of the 3-methoxy group which couLd disfavour abstraction of hydrogen from C-3 in the intermediate zwitterion [178], see aLso [143]. OnLy starting materiaL has been recovered from the reaction of FpCH 2 CH=CH 2 with four equivalents of CH=CCOOCH 3 in dimethyLformamide at room temperature for 80 h [172]. 78.…”

“…SimiLarLy, compound LXIV has been obtained from FpCH=C=CH 2 [69] and compLex LXV from FpC(=CH 2 )CH=CH 2 in refLuxing CH 2 CLCH 2 CL after 2 h [200]. The cycLic adducts LXVII (mixture of diastereomers) are formed by the reaction of FpCH 2 CH=CH 2 with R1R 2 C=CHR3 (LXVIa to LXVlg [172]; LXVlb,d [143]; LXVlg [99,175]), generally in CH 2 Cl 2 at room temperature for 1 to 20 h. An exception is the reaction of FpCH 2 CH=CH 2 with (CH300C)2C=CHCOOCH3 which does not proceed in CH 2 Cl 2 or in THF, but gives a good yield of LXVllc in dimethylformamide after 90 h [172]. see also [143].…”

Allyldicarbonylcyclopentadienyliron

“…Allyldicarbonylcyclopentadienyliron (hereafter referred to as allyl-Fp) is a 1,3-dipole equivalent which undergoes [3 + 2] cycloaddition reactions with electron deficient alkenes (eq 1) to give high yields of the corresponding cyclopentannulation products. 7 The reaction occurs in two steps. Initial attack of the γ-carbon of Cp(CO) 2 Fe(CH 2 HC=CH 2 ) on the electron-deficient carbon atom generates a zwitterionic iron alkene complex (1), which collapses to form the metalated cyclopentane product (see eq 2).…”