Vinyl Lactone Quenching

Figure 3.4 Vinyl lactone quenching, (top) Termination of a living ROMP with 3H-furanone yields a polymeric carboxylic acid end group, (bottom) Termination with vinylene carbonate resulting in a polymeric aldehyde end group.

A combined approach involving sacrificial synthesis to install the functional focal group and vinyl lactone quenching to install the terminal functionality was also reported. After acidic hydrolysis of the first sacrificial block, hetero-telechelic polyfnorbornene imide)s were generated with either a terminal aldehyde group in the case of vinylene carbonate termination or a terminal carboxylic acid group in the case of 3/f-furanone termination. 

Fuchs et al. have reported that their study on the ozonolytic reactivity of transposed cyclic vinyl phosphonates attempted to probe the anticancer SAR (structure-activity relationship) of a series of computer-designed (-i-)-discodermolide analogs [85] (Scheme 41). Ozonolytic cleavage of 200 and 201 in the presence of O3 followed by quenching with Me2S provided 202 and 203 along with the desired lactones 204 and 205 as minor products in a 6 1 ratio. Addition of catalytic DBU to 203 could drive lactonization to completion giving lactone 205 in excellent yield. As aldehyde 202 was less tolerant to DBU, it required a dropwise addition of NaHMDS in the presence of p-nitro-benzaldehyde to trap the expelled diethyl phosphate. 

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