Rhodium(I)‐Catalyzed Intramolecular [5+2] Cycloaddition Reactions of Alkynes and Allenylcyclopropanes: Construction of Bicyclo[5.4.0]undecatrienes and Bicyclo[5.5.0]dodecatrienes

Abstract

Highly strained cyclopropane derivatives have served as useful and powerful C 3 building blocks [1] for the construction of various ring systems, and the metal-catalyzed cleavage of the activated carbon-carbon s bond of the cyclopropane ring [2,3] [3c,g,j] This method [3,4] was successfully applied to the [5+2] cycloaddition reactions of allenes [3e,f,h] as well as alkenes [3b,d,g,j, 4a] as an alternative carbon-carbon p-counterpart. In sharp contrast to the extensive investigation of vinylcyclopropanes, [2b,c,e, 3-5] very few examples [6] of the ringclosing reaction of allenylcyclopropane, which is regarded as an alkylidene homologue of vinylcyclopropane, have been reported. Two representative examples are shown in Scheme 1; one involves the Rh I -catalyzed cycloisomerization [6b] of allenylcyclopropanes into a-alkylidenecyclopentenes, and the other is the formation of the a-alkylidene-3-cyclohexen-1-one frameworks by the Ir I -catalyzed carbonylative [5+1] ring-closing reaction [6c] of allenylcyclopropanes.Our continuing interest in the field of the [{RhCl(CO) 2 } 2 ]-and [{RhCl(CO)dppp} 2 ]-catalyzed cycloaddition reactions of phenylsulfonylallenes [7] prompted us to investigate the intramolecular cycloaddition reaction between phenylsulfonylallenes that contain a cyclopropyl group at the allene terminus and alkynes. Herein, we describe the preliminary results of the Rh (Table 1, entry 1).[8] This ring-closing reaction even occurred at room temperature to give 2 in 57 % yield, although a more prolonged reaction time (24 h) was required ( [3c] in which an internal alkyne consistently and efficiently afforded the corresponding ring-closed products, whereas no [5+2] cycloScheme 1. Metal-catalyzed ring-closing reaction of allenylcyclopropanes.

Rhodium-Catalyzed Intra- and Intermolecular [5 + 2] Cycloaddition of 3-Acyloxy-1,4-enyne and Alkyne with Concomitant 1,2-Acyloxy Migration

“…5 The [5+2] cycloaddition of vinylcyclopropanes (VCPs) and alkynes (eq 1), a remarkable homo-Diels-Alder reaction, could be realized by different transition metal catalysts developed in the research groups of Wender, 6–8 Trost, 9 Louie, 10 Fürstner, 11 Yu, 12 and Murai. 13,14 The significance of the intramolecular [5+2] cycloaddition of VCPs and alkynes was highlighted in the synthesis of several natural products. 15 The mechanism of this novel cycloaddition was extensively investigated by Houk, Wender, and Yu.…”

“…Although various catalysts were discovered for the intramolecular [5+2] cycloaddition of VCPs and alkynes, 6,9–13 only few examples of intermolecular counterparts are known due to challenging chemo- and regioselectivity issues. 7 The first Rh-catalyzed intermolecular [5+2] cycloaddition was developed by Wender’s group utilizing an activated vinylcyclopropane.…”

Recent Developments in the [5+2] Cycloaddition

“…In this area, Mukai et al have recently investigated the intramolecular [5 + 2] cycloaddition of allenylcyclopropanes 21a-f and alkynes. [20] These reactions were induced by catalysts such as [RhCl(CO) 2 ] 2 or [RhCl(CO)dppp] 2 , which led under mild conditions to the facile formation of the corresponding bicycloA C H T U N G T R E N N U N G [5.4.0]undecatrienes 22a-f. As shown in Scheme 9, a series of variously functionalized phenylsulfonylallenes provided the cor- responding cycloadducts in generally good yields. On the other hand, in the case of malononitrile 21d, compound 21c incorporating a simple alkyl tether between two reaction centers, and the oxygen analogue 21e, the corresponding cycloadducts 22d, 22c and 22e were formed in moderate yields of 53%, 65% and 60%, respectively.…”

3-Acyloxy-1,4-enyne: A new five-carbon synthon for rhodium-catalyzed [5 + 2] cycloadditions

“…Murai extended the 5-carbon component to allenylcyclopropanes for the preparation of 6-7 fused bicyclic compounds [27]. Hetero-(5+2) cycloadditions were also reported by Wender [28] and Zhang [29] using cyclopropyl imine and vinyl epoxide as the 5-atom component, respectively.…”