Propellanes solvolysis

In the early days the most direct method for the preparation of [m.n.l]propellanes was not yet known. Therefore the early methods involved solvolysis of suitable substrates. The first cases appear to be the preparation of derivatives of [4.4.1 ]propellanes (i.e. m = n = 4) from a compound containing a good leaving group and a suitably situated double bond. Thus the triterpene derivative (1) was used which gave a [4.4.1]propellane involving rings C and D of the educt 2. ... 

Thus the rates of solvolysis of various 3,5-dinitrobenzoates (ODNB) of 11-hydroxymethyl derivatives of [4.4.1]propellanes of different oxidation states all fall within a factor of 10 The same holds for various epimers of the same derivatives of 10-hydroxymethyl-(also on the bridge) derivatives of various [4.3.1]propellanes of different oxidation states. The rate difference between the extremes (50 and 51) was 80 The authors attribute the difference to conjugative factors . 

Work has also been done on solvolysis of syn-8-tosylates in the [4.3.1] system (syn-with respect to the cyclopropane ring) S and in epimeric, syn- and anti-7-p-nitrobenzoates of [4.3.1]propellane and in syn and anti-6-p-nitrobenzoates of [3.3.1]propellane. ... 

Solvolysis of a series of benzo[4.3.1]propellane p-nitrobenzoates substituted in the aromatic ring is interpreted in terms of a homonaphthalenium cation. ... 

In a silver ion assisted solvolysis of the dibromo[3.3.1]propellane 55 in acetone, a mixture is obtained with a surprising product (56) albeit only in 1.2 % yield, accompanying... 

The mechanistic details of the silver-ion-assisted solvolysis of em-dihalogeno-propellanes has attracted further attention and the route suggested by Warner and Lu in 1975 has been substantiated for compound (179) (Scheme 21). It appears reasonable to assume the operation of a similar pathway in related substrates that are no more strained. However, in more severely strained cases, the initial formation of a transoid bridgehead olefin is not favoured and, for compound (180) at least,... 

Solvolysis of ll,ll-dibromo[4,4,l]propellane (55 X Br) in acetic acid-sodium acetate gave a mixture of bicyclo[5,4,0]undec-l(7)-en-2-one (36%, also the major product in water-acetone), 6-bromomethylenecyclodecanone (19%), and benzo-cycloheptane (21 %). A mechanism to account for the formation of the first two products involving the strained rra/is-cycloheptene derivatives (56 R — H, Ac, n = 2) was proposed and supported by rearrangement of the labelled dichloropropellane... 

C-1. The product distribution was found to depend upon the amount of water present in the system, more 6-(bromomethylene)cyclodecanone being obtained with less water present. This observation was explained in terms of capture of the carbonium ion formed from (56 = 2). There would seem to be no examples yet where an intramolecular shift process competes with ring-opening of a cyclopropyl cation. Solvolysis of 10,10-dibromo[4,3,l]propellane in acetic acid-sodium acetate-acetic anhydride gave products formed via the strained bicyclic acetate (56 n = 1, R = Ac). In the absence of acetic anhydride products derived from the corresponding alcohol (56 n = 1, R — H) were obtained as well. Solvolyses of 10,10-dibromo[4,3,l]propell-3-ene in acetic acid-sodium acetate, in the presence and absence of acetic anhydride, and in acetic acid-silver perchlorate, were also reported. Most of the products may have been formed by reaction pathways similar to those observed for (55). ... 

Bridgehead olefins (834 n = 3 or 4) are formed in the solvolysis of the dibromo-propellanes (833 n = 3 or 4) by loss of halide anion, electrocyclic cleavage of the cyclopropane ring, and solvent capture/ The products isolated depend upon the precise reaction conditions in the case of (833 n = 3) acetolysis affords (835 53%) and (836 18 %) provided that water is not present. The details of the mechanism of the Ag" "-assisted solvolysis of (833 n = 4) have been elucidated with the aid of labelling. " ... 

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