No abstract

The neutral complexes [(η6-p-cymene)RuCl2(PPh2C⋮CR)] (R = Ph 1, tBu 2, (4-CH3)C6H4 3, (4-C⋮CPh)C6H4 4, (4-CN)C6H4 5) have been synthesized by reacting [(p-cymene)RuCl2]2 with the respective alkynylphosphine. Treatment of 1−5 with AgOTf or TlPF6 and the corresponding PPh2C⋮CR allows the preparation of cationic bis(diphenylphosphino) compounds [(η6-p-cymene)RuCl(PPh2C⋮CR)2]X (X = OTf; R = Ph 6, tBu 7, (4-CH3)C6H4 8, (4-C⋮CPh)C6H4 9, X = PF6; R = (4-CN)C6H4 10). All complexes have been characterized by analytical and spectroscopic methods, by cyclic voltammetry, and in several cases (3 and 7) by X-ray crystallography. Reactions of both neutral (1−4) and cationic (6−8) complexes with [cis-Pt(C6F5)2(thf)2] (thf = tetrahydrofuran) gave heterobimetallic neutral [(η6-p-cymene)ClRu(μ-Cl)(μ-1κP:η2-PPh2C⋮CR)Pt(C6F5)2] (R = Ph 11a, tBu 12a, (4-CH3)C6H4 13a, (4-C⋮CPh)C6H4 14a) and cationic [(η6-p-cymene)(PPh2C⋮CR)Ru(μ-Cl)(μ-1κP:η2-PPh2C⋮CR)Pt(C6F5)2](OTf) (R = Ph 15, tBu 16, (4-CH3)C6H4 17) derivatives stabilized by a mixed Cl/PPh2C⋮CR bridging system. The molecular structures of 12a and 17 have been confirmed by X-ray diffraction. However, the neutral complexes 11−14 existed in solution as a mixture of isomers [(η6-p-cymene)ClRu(μ-Cl)(μ-1κP:η2-PPh2C⋮CR)Pt(C6F5)2] (a) and [(η6-p-cymene)(PPh2C⋮CR)Ru(μ-Cl)2Pt(C6F5)2] (b), respectively.

Syntheses of the potent sulfur-containing tetrapeptide mimetic farnesyl transferase inhibitors B956 (22) and B957 (23) are described. The two double bonds in 22 and 23 were constructed by application of iterative NHK and cuprate S(N)2' reactions. Normal syn NHK reaction and substrate-dependent syn and anti-S(N)2' diastereoselectivities accompanied by exclusive E-olefin selectivity were observed for the first NHK iteration (1 --> 4). In the second iteration, unexpected epimerization and a strong preference for syn diastereoselectivity was observed for the NHK reaction (5b --> 7a + 9a) while an unusual Z-olefin was observed for the S(N)2' reaction (7b --> 11). Deprotection conditions were optimized to ensure high purity and yield of the final aminothiol compounds.