“…When the intermediate 74 was allowed to stand at 20 °C for 48 h before the addition of the second equivalent of tetrachloroorthobenzoquinone, a rearrangement occurs which facilitates a new reaction coordinate leading to the formation of 77 (9% yield, 31 P δ, 59.3 and -137.6 ppm, 2 J PP ) 21.4 Hz, eq 57). 128,129 The X-ray crystal structure of 77 (Figure 39) 128 shows a distorted octahedral six-coordinate phosphorus center possessing three chelates of ring sizes four, five, and seven. The major distortions derive from the strained four-membered ring.…”