Asymmetric diels-alder reactions : facile preparation and structure of sulfonamido-isobornyl acrylates

Synthesis of camphor-derived chiral auxiliaries and their application in asymmetric Morita-Baylis-Hillman reactions

“…Similar reaction of N,N-dicyclohexylcamphor-10-sulfonamide (6j) afforded two products: Fraction 1. The known N,N-dicyclohexyl-2-exo-hydroxybornane-10-sulfonamide (7j) 7 as white crystals (62%). 1,26.4,32.7,and 32.8 (cyclohexyl CH2),27.4,33.5,38.1,5,6,10),7).…”

“…White crystals (0.39 g, 1.0 mmol, 67%), mp 82-84 °C (Found: MH + , 378.1747. C20H28NO4S requires, M+1: 378.1747); max (ATR)/cm -1 1706 (C=O); δH (400 MHz; CDCl3) 0.82 and 0.99 (6H,two s,8,series of m,5,6,2.81 and 3.43 (2H,AB system,J 14.0 Hz,4.25 (2H,d,J 6.0 Hz,PhCH2),4.57 (1H,br s,NH),5.04 (1H,m,5.79 (1H,d,Jcis 10.4 Hz,6.09 (1H,dd,J 10.2 and 17.4 Hz,6.33 (1H,d,Jtrans 17.6 Hz,7.33 (5H,overlapping signals,ArH);δC (100 MHz;9),27.0,29.8,5,6),47.2 (PhCH2),7), 51.9 (C-10), 77.9 (C-2), 128.9 (C-2′), 127.97,128.0,128.8,and 137.0 (ArC),. 9 and 20.3 (C-8,9), 27.0, 30.2, and 39.5 (C-3,5,6), 37.7 (C-2′), 39.1 (C-3′), 44.4 (C-4), 49.1 and 49.7 (C-1,7), 50.9 (C-10), 78.4 (C-2), 117.…”

“…9 and 20.3 (C-8,9), 27.0, 30.2, and 39.5 (C-3,5,6), 37.7 (C-2′), 39.1 (C-3′), 44.4 (C-4), 49.1 and 49.7 (C-1,7), 50.9 (C-10), 78.4 (C-2), 117. 7,119.6,125.0,130.7,135.4,and 138.3 (ArC), 168.9 (C-1'). Similar reaction of crude 2-exo-hydroxy-N-phenylbornane-10-sulfonamide (7c) afforded two fractions: Fraction 1.…”

“…Reduction of the carbonyl group in each of the N-substituted camphor-10-sulfonamides 6a-j was effected using NaBH4 to afford the epimeric 2-hydroxybornyl-10-sulfonamides 7a-j and 8a-h,j in moderate to excellent yields (53-100%) and, generally, with high diastereoselectivity 100% in the case of the 2-imidazolyl derivative 7i), as shown in Table 1. The dicyclohexyl derivative 7j has been used previously as a chiral auxiliary by Oppolzer et al in asymmetric DielsAlder reactions 7 and in the asymmetric synthesis of aldols, 8 halohydrins and epoxides, 9 and α-amino acids. 10 Semi-preparative HPLC permitted isolation of analytical samples of the 2-exo-and 2-endo-hydroxy epimers, eight of which are new compounds.…”

X‐Ray Structure Analyses of Alkyl‐Substituted N‐Acryloyl‐ and N‐Crotonoyltoluenesultams

“…The N-lone pair (lp) is believed to be anomerically directed and stabilized, in the absence of major steric interactions, by the anti-periplanar S=O bond 191 1141, although, for N-acylbornanesultams, neither systematic lengthening of the S-N nor shortening of the S=O(l) bond lengths could be demonstrated [14]. According to this hypothesis, one would expect the N-lone pair to be anti-periplanar to the pseudoaxial S=0(2) bond in (-)-la, but this would bring the N-enoyl chain close to both pseudoaxFor planar and pyramidal acyclic sultam X-ray structure analyses, see [12] In conclusion, the structural differences between N-enoyltoluene-and N-enoylbornanesultams are mainly due to the possible loss of the pseudo-C, symmetry. This results in a decrease of the stereoselectivity observed for the uncatalysed [ (-)-la in the anti-s-cis conformation9).…”