2,3 -Bis cuprate

The conversion of the dehydrotrimer 135 into the corresponding bis-cuprate followed by coupling with dibromide 131 (Cadiot-Chodkiewicz conditions) gave the expanded [5]pericycline 122 in 53% isolated yield (Scheme 28) [4]. The more versatile approach by simple oxidative cyclooligomerization of dehydrooligomers of type 135 under high dilution conditions as shown in Scheme 28 provided the acetylene-expanded [3]- 82, [5]- 122 and [6]pericyclines 163 in reasonable to excellent yields [4,7]. 

Figure 7.25 Variation of with hole concentration in superconducting cuprate families (from Rao Ganguli, 1995). 1, 2, 6 and 7, Bi cuprates 5, 123 cuprates 3, Laj- Sr CuO, 4, T1 cuprates. The variation of normalized with is shown in the inset (From Zhang Sato, 1993).

The common manifestation of two underdoped state pseudogaps is expected theoretically. This has been recently established experimentally for the La and Bi-cuprates [31-35], The small pseudogap is known to develop smoothly from the larger superconducting gap [18,31,32], That is comparable with the transformation As <- Arat Cp. 

The same cyclic pentamer was prepared much more efficiently by the cross-coupling of a preformed trimer, 45, with a preformed dimer, 47 [22, 31]. This was accomplished by separately converting the trimer to the corresponding bis-cuprate, 46, and the dimer to the bis-bromoalkyne, 48, and then mixing the two in pyridine under dilute conditions (Fig. 9-13). In this way, the five-sided macrocycle, 44, could be isolated in the greatly improved yield of 54%. 

Elongation of acyclic dimer 47 at both ends, using the method encountered so frequently in Section 9-2, followed by oxidative cyclization gave the 16-membered ring hexayne 70 in 14% yield (Fig. 9-20) [22]. An alternative synthesis of the same macrocycle via a bimolecular coupling between the bis-cuprate of 37 and dibromo compound 67, according to the method in Fig. 9-19, worked in only 2.6% yield [22]. 

A new method for spiroannelation involves the double conjugate addition of the bis-cuprate reagents (33) to /8-halocycloalkenones (Scheme 11) ... 

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