Cycloaddition of chlorosulfonyl isocyanate

An approach to biotin [166] starts from a [2 + 2] cycloaddition of chlorosulfonyl isocyanate to chromene. The excellent regioselectivity of this reaction may be attributed, at least in part, to the ethereal oxygen. 

Starting from the commercially available (+)-3-carene, the cycloaddition of chlorosulfonyl isocyanate [228] has been reported to furnish the enantiomeric (3-lactam in a regio- and stereoselective manner [229]. Treatment of the (3-lactam with di-ferf-butyl dicarbonate resulted in iV-Boc (3-lactam, that could be readily opened under mild conditions (Scheme 104). 

The 2 + 2-cycloaddition of chlorosulfonyl isocyanate with chiral alkoxyallenes, derived from ethylidene and benzylidene L-erythritol and D-threitol, produces azetidi-nones that are readily converted into the corresponding tricyclic cephams. NMR and CD spectroscopy were used to assign the absolute configurations of the azetidinones... 

Graf [103] originally proposed a two-step mechanism for the cycloaddition of chlorosulfonyl isocyanate to alkenes. This leads to the 1,4-dipole shown in Eq. (5-35), which can then ring close to give a y9-lactam (and as by-product an unsaturated amide via a proton shift from R or R to N ). Moriconi [104], on the other hand, has proposed a nearly concerted, thermally allowed +, j2a] cycloaddition, probably initiated by a r-complex formation, and proceeding through the dipolar activated complex shown in the lower part of Eq. (5-35). 

FIGURE 10.1 Diasterofacial differentiation in [2+2]-cycloaddition of chlorosulfonyl isocyanate with carbohydrate vinyl ethers 47. 

Kaluza, Z, Furman, B, Patel, M, Chmielewski, M, As3fmmetric induction in [2 + 2] cycloaddition of chlorosulfonyl isocyanate to l,2-0-isopropylidene-3-0-vinyl-glycofuranoses. Tetrahedron Asymmetry, 5, 2179-2186, 1994. 

A key intermediate in carbapenem antibiotic synthesis has been prepared through a highly stereoselective [2 + 2] cycloaddition of chlorosulfonyl isocyanate with an optically pure 1,3-dioxin... 

The 1,2-dipolar cycloaddition of chlorosulfonyl isocyanate to different cycloalkenes has become a well-known route for the synthesis of cycloalkane-fused p-lactams, and for alicyclic P-amino acids, after hydrochloric acid treatment. The addition takes places regio- and stereospecifically, in accordance with the Markovnikov orientation rule [51-55]. In this manner, a number of homologue and analogue alicyclic P amino acids have been prepared, such as czs-2-amino-2-methylcyclopentanecarboxylic acid [56], m-2-amino-2-methylcyclo-hexanecarboxylic acid [56], (l/ , 2S, 4S )2-amino-4-terMnitylcyclopenta-necarboxylic acid [55, 58], 3-exo-aminobicyclo[2.2.1]heptane-2-exo-carboxylic acid [59, 60] and 3-exo-aminobicyclo[2.2.1]hept-5-ene-2-exo-carboxylic acid [61]. 

The study of [2 + 2]cycloaddition of chlorosulfonyl isocyanate (CSI) to a variety of l,2-0-isopropylidene-3-0-vinyl-D-glycofuranoses (Scheme 32) showed that the observed high selectivity of these reactions was steri-cally controlled and depended on the size of the substituent at C-5 of the sugar [89]. The /3-lactams 113 and 114, obtained from vinyl ethers 112, were transformed into the corresponding cephams 115-118 by the intramolecular alkylation of the j6-lactam nitrogen atom [89,90]. [2 -I- 2]Cycloaddition of CSI to (Z) and (E) vinyl ethers proceeds stereospecifically with asymmetric induction in the range reported for simple vinyl ethers to afford corresponding cis and trans /3-lactams [91,92]. 

A theoretical study of the catalytic and substituent effects on the 2 - - 2-cycloaddition reactions between isocyanates and aldehydes was presented. Steady-state NOE coefficients have been used to develop a stereochemical model for the transition state for 2 -I- 2-cycloaddition of chlorosulfonyl isocyanate with chiral vinyl ethers. The asymmetric 2 -I- 2-cycloadditions of chlorosulfonyl isocyanate to chiral vinyl ethers derived from sugars and hydroxy/acids have been reviewed. 

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